Display art by category

[omartan]

It'll be nice to be able to only display artwork from certain categories only

[michealparks]

@wheelhot This is a great idea, but it's one that seems like it'll be a little far off down the pipeline since galeri's sources are limited to a few museums and art styles at the moment. We want to have a deep well to draw from in each category so we'll need to spend some time researching and adding additional open museum image sources before doing this.