the problem with that is if I align the thumbnails on one screen size on one theme it will be out of alignment on another. As you shrink your browser it pushes a thumbnail off a row and leaves a giant gap on the right hand side, (this behavior happens on every theme). I cant set different sized thumbnails for different screen sizes, or browser widths.
being able to center thumbnails might alleviate this issue, because when a thumbnail gets pushed off a row the thumbnails would still be in the center of the page.
Thanks again for your continued help!