He [Matt Cutts] talks about writing quality content. Every time I read one of his Panda posts, he always talks about content as though it can only be textual. He never talks about what image heavy websites should do.
That's probably because Google Web Search (as opposed to Image Search) is largely about textual content. There may be ways to improve an image-heavy Web site's Google rankings in the post-Panda era, but for Google Web Search, images are likely to be treated as icing on the cake, not the cake itself.
If the artists don't want to write about their works, can you? Maybe you could set up a simple questionnaire for each artist (and each work) that could be used to create a mini-interview and catalog description?