I'm repeating what I wrote earlier in the comments. The painter is italian, going by its names. A twirly moustache would go well on him. Besides that, messier clothes, with paint stains all over it. Perhaps his cap could be replaced by one of those big puffy bonnets, leaning into his more artistic side.

the painter could perhaps have a bob-ross inspired look, and the tavernkeep would be more interesting with a more exaggerated body shape/build. maybe you can communicate more of the princess' elegance with some outfit changes, too.

(Sorry, I've been busy irl for a while - thanks for the ideas to both of you!)

A beret and striped shirt might be in order for the painter. Maybe make him a little slimmer as well. The princess might look good in a ball gown. And/or possibly recolored blue.

As for the tavernkeep... tough one. The chef look might work. Something a little more stereotypical and a little less Gordon Ramsey-ish. Or I guess you could always turn him into Moe Syzslak for a lark.

simple
tavern keep=he perfect
painter=add paint blot's onto him
princess=give them there scepter

For the tavern-keep, maybe some beer stains on his apron, as well as a design to fit with the rest of the overhauled npcs, just adding some more details and such.

For the painter, maybe some paint on his overalls and shirt, maybe on his cap as well. Along with maybe some hair poking out from below the cap.

For the princess, maybe just a detail overhaul, like a jewel in the crown and a touch up on the details, maybe adding a slight gradient to the dress, from purple at the end to pink at the top

seconding the princess scepter idea! maybe something royally adventurous? like she's been inspired by the terrarian's exploits to take up monster fighting or somethin, and yoinked some armour from the gaurdsmen back home to chase gloryprotect her kingdom from threats.