Design for app currently in development

I'm building a site that integrates with facebook login/users/notifications and allows users to buy/sell things in their areas for free. The site doesn't have a name at the moment but the working title is Sellapp. I've build Balsamiq mockups of the 6 main pages that I need built. I'd like someone to take care of actually making it look pretty, giving it a logo, a theme and consistent styling throughout. Also don't take my mockups as the law, feel free to make the ideas in them more useable and better :) I'd like you to come up with some rough ideas for logo/theme and send them to me before we make any progress on to the full design, which will be delivered as illutrator/photoshop files.