So, checking it out:
Yes, you'd really want another build to start with. Preferably something smaller. If it hadn't been for me wanting to check it out, I'd have left because with draw distance set to 64m (slooow machine), I can't see all of the shop. Something that has some contrast added, maybe a few more colors instead of having it all one in one. It's easy to get lost in the place and not see everything due to the design. Look at some of the more well known places (SiniStyle is a great example for a fitting look of shop and items sold, Nyte 'n' Day has a nice, but also too big place, Mischief is maybe rather close to what you're looking for).
Don't use vendors. Ever. Size down color choices, maybe. NO Vendors. Don't do it.
As for the boxes. Redo them. Maybe let somebody who has had some experience with
SL photography/advertising help you. I wouldn't want to buy anything from your place, as far as I have seen it. Make the ads more of eyecatchers, add some smiling, (state of the art) models, add contrast to the pictures and make them stick out. Use neutral backgrounds that preferably do not change between the different items, or at least not between the different categories. Get rid of the JPEG artifacts.