Actually I am using a specific application to sell my photo works , it is Sytist , a grate tool , has the option for manage all image data for galleries and for selling on Amazon S3 , but it is not WordPress Compatible, no multisite compatible, it is a stand alone application that must be installed on server , no problem about that and works really nice on my cloud vps

I am photographer but I also give technical support in a photo lab , almost 90 % of clientes has on this days his own web, managed by themselves or by external companies .
The interesting option that I could give them with the appropriate gallery plugin is to give – rent – sell a personalized WordPress web portfolio- gallery- blog that allows sell their job online, but its a must to store some thousand of files externally from main host.

So Thanks a lot for your attention .