I suggest adding a "tag" feature to the posters. In addition to the band names, and designers names, have a field for tag words. For the existing database, let users add tags for description.
If there is a band you've never heard of, and a designer You've never heard of, you may likely never see a specific poster that is otherwise fantastic.
A poster like this one below might read have tags for:
bird, news print, hand drawn, white, brown
You could do a search for "clown", and all posters tagged with "clown" would turn up in the results.