There are a number of approaches you can take to setting up an online photo display site. You can focus on artists, photographers, or the general public. If you focus on artists, you would generate revenue by charging them a fee to have their work displayed on your site. This would assist them in selling their original pieces of work.
Alternatively, if you focus on photographers, you can earn revenue on a commission basis or by a flat fee. You could allow photographers to submit images to your site. In turn, you would sell access to your site to the consumer market. People would pay for the license rights to the image and in turn you would pay the photographer and retain a percentage.
The third option is to open a photo display site to the general public where people could create their own folders and upload their own images for free. Revenue would come from complementary products and services. Photopoint.com is one such example. They sell cameras, printers, postcards, photo prints, and so on.
If you need more advise to setup this business, please contact me at email@example.com