Yeah great idea, there's just one thing that kinda ticks me off about these sites, peoples themes are uploaded without their knowledge and the only credit visible is the uploader.
This would prevent someone like myself (who takes great care when making something), from using said site as people can just easily take credit for someone else's work. I quickly found my henkaku theme on your site without my knowledge or consent (nor any indication where it came from or who made it)
If anyone expects any of these theme repositories to succeed, it has to be way less wild west about how you upload and make it so that you don't step on the toes of the people who spend their time doing these things.
I love the idea, but honestly if you want to include something made by someone else, the VERY least you can do is inform them.
Other than that,the site seems good, it's easy to use and understand, I would though personally prefer 2 or 3 screenshots of the themes (But I suppose you are trying to make it easy to use in the Vita browser)
If you would care to remove my themes the site, I would be happy to register and actually use it myself.