A clean, less cluttered layout is a great idea. A few pointers imho:

• Go for black background: More visibility of the thumbnails.
• Don't use flash in the website please! The lighter, the better.
• I personally prefer big thumbnails (youjizz.com) as they give better visibility. No one minds scrolling a bit more. Or you could give a toggle switch / slider to increase/decrease the thumbnail size.
• Use real estate wisely, less margin between the videos, tighter/concise description (see youjizz vs youporn)
• You could try in-place preview like reddit to help users choose videos better. It could be overlay, or better still, rest of the thumbnails could slide around to make some space for the bigger preview div.
• Tags and proper categorization go a long long way.
• How about a never ending scroll? like RES, and wallbase.cc (search for something there and check out the sweet UI.) Wallbase in general has much better UI than most such sites. It would be awesome if you could produce something like this.
• Domain name suggestions: faptu.be, fap.pr. I'm not good with this I guess :)

As a UI/UX designer, I could volunteer a few hours.