First off, Excellent domain. I love it alot. Ok, now that we got that out of the way...Get content up! You have lots of empty pages there that could be filled. I know white space is in, but not completely blank

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Colors...Colors right now are VERY fast. By fast I mean they make the user want to move on. Blues and greens are more soothing, and more likely to make users stay on the site longer (hence maybe buy more). Red, oranges, and yellows are fast colors that make users want to leave and get through the site fast.
Navigation...Simple. It's laid out well, and easy to use. Very well done.
Shopping cart...Maybe offer a close up of the image that will go on the shirt as well as the thumbnail. And what is "ENTER YOUR PRICE"? Do the customers make up a price? That part confused me.
The site itself has a california sirfer feeling to me. I like that and think it can be successfull if the colors changed some, and content was added