It depends on how you insert your gallery. You have to change your Gallery Style CSS (nggallery.css), maybe it’s the appearance in this part .ngg-galleryoverview
I like your website, very nice. How did you place the images in your pages? Are they programmed manually? Can you give me a hind how to connect the link / image with the gallery? I can’t identify the relevant parts of your web-code
Here is a way to protect your changes from updates. Maybe you haven’t seen.
http://nextgen-gallery.com/templates/
thx Marcus