The problem with this link, shared by Elizabeth Barrette, is that you have to have a Dreamwidth account to propose a topic and style of poem for Finch to write. In other words, you don't have to give Finch money, but you have to give Dreamwidth money? Cold prickle.
Anyway, this page is good for a list of topics with which other poets (or prose writers or artists) might want to play. "Elegy for a crow" caught at my imagination. Maybe some other "prompt" will inspire you.