Artists are not helper monkeys; they’re not in it to visualize 'your' story, because it stopped being 'your' story the moment you engaged in a collaborative medium. From here on in, it’s also the artist’s story, and if you’re working with an illustrator who’s any good at all, you as a writer have to tamp down any control-freak tendencies you suffer under and relax into the process.
Mark Waid