Hi Diego,
I suppose that the photography itself should be the most important thing that makes someone buy it, isn't it?. I'm sorry that you didn't find it on my webpage.
Because primarily the flash presentation, for me, doesn't work. (I mean it functions OK, but I guess, psychologically, your site is exercising too much control over what _I_, perhaps a potential customer, wants to do, and then, if I want to buy, a page of complicated hoops to jump through - just not worth it for a $5.00 purchase of an image that I can't even see properly. You yourself have mentioned about the poor resolution, etc. and folk are used to simple shopping cart purchases, paypal and the like. If you have not grabbed the attention in the first few seconds, they will go elsewhere.
The two images you linked to, come over much better. But these should never be sold for $5.00. This sort of quality needs to be sold differently, if you want to maximise your profit.
It is one thing to be able to take good/perfect photos. It is quite another to market and sell them.
I think we must be brutally honest with ourselves. Ask and answer a lot of questions, along the lines of-
1) why do I need a web site?
2) if I need it, what is it's purpose?
3) am I good enough at web design to get that purpose across?
4) how do I drive the people that I want to see my stuff, to my website?
For example, you see the background to the two images you have linked, the history, the significance of the location. Just a paragraph or two on the trees, or the balls, would make the difference to potential purchasers. Folk would be buying into something more than a collection of coloured dots.
I have just spoken with a professional photographer who I respect. He actually sells prints from his website. He has had the site and name for ten years, he says it is because it comes up high in the search engines. A friend of his, started a similar site a year ago. similar images, prices, etc. He has sold nothing.
So, you have to do more than a flash presentation, if it was that easy, everybody would be doing it.
Best wishes,
Ray