Your web site is *really* dubious.

I can't see any licence (license for Americans?) information anywhere on the site, no snailmail address, the company details (incorporation country, numbers, etc) aren't clearly displayed.

It is really important for anyone buying any game assets, that they absolutely, definitely aren't pirated, and that is not made clear on your site. Because there aren't any details I can see which tell me even which country you're incorporated in, or that your company even exists, if I were in the position to do so, I definitely wouldn't buy anything from this web site.

NB: This is intended as constructive criticism. Presumably you have permission from all the creators of all assets displayed on this web site, to resell them (or made them personally). If so, you can probably display all the relevant legal, copyright, company details, as well as a snail mail address.

There are a lot of charlatans on the web attempting to sell other peoples' copyrighted works in violation of their licence, either ripped from other games or just plain stolen.

You need to clearly distinguish your site from theirs. I'd also recommend getting a SSL EV certificate and running it exclusively over SSL.