Best way to organize a bounty for a completely open project?

I want to organize a bounty for a completely open project. By "open" I mean that the entire development, everything produced, suppliers, code, graphics, bids, rejected bids, ideas, everything will be licensed with a Creative Commons license.

The project is for a high quality paper wallet, and will require graphic design, a tiny bit of JavaScript coding, and some parts sourcing. I will do some of it myself and offer bounties for the things I can't do. This is NOT the bounty post, I'll do that next. Here I'm asking for advice on organizing a bounty.

I've seen other bounties where concerns were raised over payments and delivery, over licensing etc. I want to make this easy and open. I'm willing to do escrow, let the community pick the best designs, code, etc for the bounties, whatever it takes to make it successful and get maximum re-use of anything created.

Suggestions?