Cool work Chris. To be honest I'm wondering why you'd want to group your content in the first place, right now it feels a little random. Why not drop the separation and make the thumbnails equal sized? The fact that the imagess are opening in the same tab isn't very elegant, people have to click the back button way too…
When I click on a gallery the tabs are titled "Untitled Document" if you go to page properties -> title in dreamweaver you can fix that, I think it's important because I first thought when clicking it was only opening up one image by itself (due to the white background too which I think should match your main site bg) so…