I want to second undunoops' idea of artists producing their work first: *seconds firmly*
I'm frequently inspired to write by art, and, as a writer, I like the idea of having the art as a jumping off point in a collaboration because my final draft is never the same as my first—last Games, in fact, I scrapped three very long and different fics in favor of a short one which I felt was more complete and better suited my prompts. In a collaboration in which I had to produce my offering first, any artist with whom I worked would no doubt end up feeling hella jerked around, and that wouldn't be fun for either of us.