Where is the best place to sell images files for download ?

Answer 1

I think you are going to have to judge for yourself, but here are some options to check out:
Shutterpoint.com says they have members submit over 2,000 photos a week. Their fee is 15%.

Buypixel.com charges 40%

IStockphoto.com, mentioned in the prior answer, charges 80%, unless you give the exclusivity and then they only charge 60%.

There are other considerations like how busy the sites are, what requirements they have of the photos. I think you should investigate and decide for yourself.

Answer 2

http://www.istockphoto.com/ pays you royalties every time someone downloads you photos that you upload.