Hi, I've registered just to give you some feedback on this plugin. I'll start with critical bug, that makes the script unusable for me:
1) Once you get 36 pictures into cart(37 different images, not 1 image with value 37 in quantity) and try to add 37th new picture will overwrite 36th in the cart. Always. This means that once you get to 36 pictures in the cart you cannot add any more. Cart shouldn't be filled with just that

There's no setting for max number of files per order, so I'm positive it's a bug.
Now, when we have that done, there are features and improvements that I would like to suggest:
1) Make it possible to set it so "Add to cart" button redirects back to the page with the picture instead of going to the cart. Also show notification "picture added", so the user will know it worked. With bigger orders going to cart every single time makes the plugin almost useless, as most users will give up after just few pictures.
2) Make it possible to "save order as draft" if you're logged in, so person can continue their order during few sessions(I know cookies remember the state of the cart, but I would like it to work between computers).
3) Make it possible in settings to activate "add to cart" button under the photos in miniature view, for quick adding.
4) Least important of all of them - ability to add many folders to the shop plugin at once. This has to be done only be admin and only once, so even though it was irritating for 200+ albums that I had on my site it's manageable.
Suggestions 1-3 are pretty important, as they increase the ease of use and make the plugin more user friendly. The easier it is to order stuff the more people will order, and the more money goes to the sellers. Even so I will be really happy if you just quickfix the 36 limit issue.