Have you got a custom theme installed?
I set up a test site, installed brand new clean WP and brand new clean Image Store, Both latest versions.
I didnt change any config at all and created an gallery – uploaded 5 pictures, looked at the site and it works normally….
I then installed my own theme (made using artisteer) and it broke the site doing exactly what your screengrab shows. Must be incompatability with a script etc but I dont know which.
I would also love to have an add to cart button underneath the image next to the select button.
Obviously I need it to work with my theme first though lol.