It's an excellent concept and your logo is great. A bit more work on the site could really improve life for your visitors and hopefully increase your sales.

1 I'd lose the frames. They're not really necessary and, in the resolution I use, they give a grey scroll bar that cuts the screen in two and spoils your design.

2 Try thinking hard about the navigation to make it more obvious. At the moment, visitors have to think where to go and some of them won't bother. Can you group the site into main sections - Gallery, info for buyers, info for sellers, about us. Then you can have further navigation within those sections.

3 Do you really need those spots. They don't really add anything and make it harder to read the text.

4 Try to make buying easier. Push taking credit card payments up your list of priorities. (Paypal is the cheapest way, Worldpay is more expensive) A shopping cart system may be outside your budget but a buy button beside each picture that takes people to an order form would be better than nothing.

5 Think hard about post and packing. Like many people, I wouldn't order without knowing how much this would cost. I know this is difficult with such a varied product range but can you at least give a guide price? (unframed prints, framed prints etc)

Good luck - this is well worth developing.