On one hand we have designers readily available, people we can hire to create something with direction or concepts already available.
On the other hand, we have sites like 99 Designs and Crowdspring to help one find the concept or direction that is right for them by getting samples from professionals.
I'm looking for the web service that falls in between. When doing illustrations or a series of designs, a company needs to find an illustrator who has the style they want though that concept may not be clear. One needs a forum through which possibilities can be evaluated for a host of designs rather than a single logo or page template.
What's the best way to find and get bids from a variety of illustrators/designers given only vague direction about the illustrations you need?