ecommerce plugin & photo Gallery

HELP…Please
1st part of the problem.
I am a Photographer I am trying to set up a photo gallery where all the customers photos run across the bottom (some times 600 or more photos). They click on one and it shows a large image of that photo.
The photo number must show all so.

2nd and biggest part of the problem.
I sell what I call mini-mags, the customer picks the photos they want for there mini-mags. My problem is they need to be able to pick
12 photos + Cover Photo or
20 photos + Cover Photo or
28 photos + Cover Photo or
36 photos + Cover Photo
I was told I need an ecommerce plugin, I have tried a few but none will let me set up for my different size of book and the other things I sell.

Can any one help?