That project will probably be tougher to place than a less art-dependent one, but it’s not impossible. It could happen in a number of ways. If you have an opportunity to submit directly to an editor, she likely wouldn’t acquire it until she gets an illustrator to commit. She’d then take you both to her editorial board as a package deal for the final okay. I’ve seen that happen plenty of times with concept book projects that hinge on the illustrations. If you submit to an agent, the agent may decide to handle the pairing herself, pitching your concept to editors with an illustrator she already represents. An option you might consider, if yours isn’t a time-sensitive concept, is holding on to it until you’ve secured an agent or editor with another manuscript, one with more textual “meat.” At that point, you’ll be talking with them about other projects you’ve got in the works and can pitch this concept. Its acquisition may still depend on an artist’s solid commitment, but you won’t be trying to land your first deal with a manuscript that’s more idea than text.