I've been doing the poem a day challenge for Poetry Month. It's often a stretch—but a good discipline.
Carl, from Arizona, where I hope it's nicer than it is here today where it's pouring, sent me this link.
While the author of the blog suggests the prompts as prods for poetry, I think they can be used as prompts for prose.
Here's an example:
16. Make a list of ten images of things you have seen in the last 24 hours. Use all of them in a poem. I'm visualizing a lyric essay.