The tables in Xanathar's Guide to Everything are great, but they're way, way too short! Happily that makes them an excellent subject for a blog post. Here are the first three classes: Barbarian, Bard, and Cleric.
The barbarian 'tattoos' table is a bit longer cuz I got carried away.
BARBARIANS
Personal Totem
Tattoos
1- a grinning shark-like maw extending on either side of your mouth and up your cheeks
2- A series of protecting runes encircling your throat and covering your heart
3- Red geometric lines, like blood streaming from the corners of your mouth
4- A random-seeming phrase in a language you don't know. To you, all writing has powerful magic potential, and when you 'liberated' this bit of script from some scholar you inscribed what you thought must be the most important bit of text onto your skin, to absorb it's magic.
5- The entire sleeve of one arm, inked a solid black.
6- The phases of the moon (or one of the moons) inked across your knuckles.
7- The name of a lover who broke your heart. Seeing it causes you great pain and anger, but you're too stubborn to get it removed or covered up.
8- A map to a secret location. Work with the DM to determine where this might be. You don't trust paper or writing, so you had this tattooed on you, and had the map itself destroyed.
9- A face tattooed on your but. The idea is that you can move your buttcheeks and make the face kind of look like it's talking. At your option, the face may be that of a famous political or historical figure, a scowling demon or dragon, or a badly rendered replica of your own face.
10- A to-do list. You didn't have a pen handy, but you did have a tattooing needle...
11- Knuckle tatts that read 'RAGE' across one hand and 'KILL' 'HATE' 'LOVE' 'DEAD' 'SMRT' 'FUCK' or some other four-letter word across the other hand.
12- Traced white lines, as if scarred by lightning.
13- A keyhole shape, around your eye, and a key on your hand.
14- A series of hatched lines; you add a new one for each worthy foe you slay in battle.
15- "MOTH" inside a heart
16- An anchor. You're a traditionalist.
Superstitions
1 - Never let an ally become entirely obscured from view during a fight or in a dungeon, or you will be suspicious of them until they reprove their trust. One way of restoring trust is by asking "what goes up a chimney?" And the other responding "smoke."
2- birds are unlucky, especially pictures of birds. You will never tolerate having a picture of a bird in a house, and if you can destroy the picture that's ideal
3- the last person to arrive for drinking has to quaff a whole drink, as a penalty. When drinking, alcohol must be poured for all present, altho they are not required to drink
4- it is bad luck to give or receive a weapon or any kind of blade as a gift. This may be avoided by exchanging a token amount, such as one silver piece, since an uneven trade is not a gift.
5- wizard's magic is weak to silver - their magic may ward off a knife, but silver will cut through.
6- things always come in threes. So if you have fallen into a hole twice, or found gold twice, you're bound to have it happen a third time
7- Someone who dies will need their weapons after their dead. Don't loot that sword off your friend, as he may be fighting ghosts with it in the afterlife. Replicas or substitutions may be acceptable.
8- money is cursed, and you will never touch it with your hands if you can help it.
BARDS
Defining Works
1- 'the Tain of Greenmere' A rambling saga - chant that recalls every river, hill and dell of a long journey across your homeland, now lost under the sea
2- an extremely experimental work, filled with invented words and seemingly stream of consciousness verses that in fact you poured inordinate amount of time into getting just right
3- a catchy hit song that you're famous for performing as part of a band of five nearly identical-looking young singers
4- its a cover of someone else's song, but your version was so defining that even the original artist has basically given it to you, going so far as to say they'd hesitate to perform it themselves without your blessing
5- 'Misummer Knights' a bawdy tale about the queen of the fairies, her clone, and a lot of nudity, chaos, fighting, and mistaken identity.
6- a conceptual art piece consisting of precisely measured long intervals of silence, interspersed by a few single notes.
Instrument
1- musical saw stolen from loggers trying to clearcut a dryad's grove
2- Balalaika, engraved with images of a polar bear grappling a moosetaur
3- Crwth made of scrimshawed whalebone
4- Aulos won from a satyr in a drinking contest
5- Nyckelharpa made by a famous firbolg crafter
6- Digeridoo fashioned from a mastodon horn
7- Ocarina with a built in watch ⌚
8- Xaphoon bound in red gold and inscribed with the sigil of your house
9- Lur with a matching helmet with decorative horns
10- A hurdy-gurdy engraved with eldritch prophecies of doom in an ancient tongue
Embarrassments
1 - Having read far more words than you've heard spoken, you frequently mispronounce rarely-used words.
2 - You completely forgot the Duke's name in the middle of the season's premiere social gathering
3 - It was discovered you'd used illusions to fill out the audience of your play 'Qouth the Zondervoze.'
4 - Interupting the production of the play 'the King in Yellow,' you wrecked the set and burned the only copies of the script before the actors could learn any of their lines. You are mocked for it, but you swear there was something deeply sinister about that writing.
5 - One does not need to explain the depth of this faux pas: You wore white after the harvest festival, but before the beginning of spring.
6 - Challenged to a rhyming duel, threw up before getting on stage- ruining your chances and your favourite sweater.
Clerics
Temple
1 - A black, basalt column sprouting from a seaweed and barnacle encrusted rock in the middle of a storm-tossed sea
2 - an idyllic grove, ringed around the hill with ancient henges of stone and wood, where wine and food is always on offer
3 - a hospital in the slum of a war-ravaged city, dedicated to administering aid to the sick and wounded.
4 - A hidden safehouse, tucked in a blind alley, impossible to find unless you know where to look, and with half a dozen secret escape routes
5 - a barn, converted into a church by the rustic folk of the village, decorated with homespun 'tapestries' and colourful murals.
6 - a sprawling, bureaucratic edifice, a brutalist building filled with clerks and auditors, filing everything in triplicate.
Keepsake
1 - A feather of ever-shifting iridescent hues
2 - A teapot, painted with one of the symbols of your faith
3 - A bedraggled doll, given to you by a child whose life you saved to keep you safe when you were headed into danger.
4 - A bottle of wine you acquired during a frankly somewhat hedonistic evening in the big city.
5 - This pocket-sized holy book still bears the scar of the arrow that would have pierced your heart.
6 - A set of manacles, which you wore during your imprisonment for the crime of following your faith.
7 - A finely crafted pen, taken from the seminary where you underwent your training.
8 - Flint and tinder- a reminder that there can be light in even the darkest places.
Secret
1 - What's the harm in making a little money performing magic on the side? Surely the gods wouldn't have given you these gifts if they didn't intend for you to use them.
2 - Whether sentimental or superstitious, you keep an icon of the spirituality of your childhood, from before you converted.
3 - Although sworn to avoid all worldly attachment, you have a secret spouse- an important figure within the government.
4 - If the gods don't grant you the miracles you need, you're not above faking them.
5 - You are writing your own treatise on religion, one you hope will eventually supplant the existing orthodoxy of your faith.
6 - A parent forced you into the clergy to avoid an inheritance complication. You never wanted to be a priest, but to everyone's surprise you manifested the gift of divine power!