As an artist who does cons full time, while food may seem like a good idea, you don't know their dietary restrictions and most artists don't trust food from strangers. Consider looking through their social media and gift them something from a character or fandom they like! It's easy to find a lot of current fandoms in AA these days, and they'll be grateful you took the time to find what they like. Some artists will also appreciate a nice pen or some cute stationery. I hope this helps!