Try adding this to the navigation section on your style sheet (in place of that prior codeset I recommended).
/*-----------------auctiva_image_border----------------*/
a.supersizelink img.auctionimage {border: 2px solid #71c1be;}
a:visited.supersizelink img.auctionimage {border: 2px solid #71c1be;}
a:active.supersizelink img.auctionimage {border: 2px solid #71c1be;}
a:hover.supersizelink img.auctionimage {border: 2px solid #3ef5f8;}
I used the matching blue and bright hover blue from your template for those border color code numbers.
Danno
BTW...very nice pro template you got there.
On the original problem of multiple supersize from single image, I'm working with script codesets for widget zoom imager (on-page zoom with NO POPUP) that I may be offering at some point in a store. I like your upper box design. With the current design, you could use a row of about six or seven 40 x 40 micro-thumbs under the image with simple mouseover to switch images and stay with that square 350 x 350 main image viewer. Code for popup supersize could be adapted from Auctiva's codeset. However, I'm trying to move away from secondary windows/popups that avoids more windows/tabs in favor of on-page animation.