Drop the "number of columns" settings (image and folder thumbnails) and the aspect ratio settings. Let the user specify the thumbnail and folder thumbnail image bounds, the maximum page width, and either fixed shape or not.

If the user wants more columns, he can reduce the thumbnail bounds and/or increase the page width.

If he specifies "fixed shape," use the aspect ratio defined by the thumbnail bounds (if the bounds are 320x240, show 4:3 thumbnails). If not fixed, use the actual aspect ratio of the images, but constrained (so that pano's don't blow up the layout). Ditto for the folder thumbnails, but start with bigger default bounds, like 400x300.

The way things are right now, the user finds himself at war with the skin. He sets bounds, but then the skin changes them, or does something unpredictable with them.

And you're giving him settings that contradict each other. "I want bigger thumbnails, but more columns, but a narrower page," or, "I want 300x300 thumbnails, but I want them to be shown in a 3:2 aspect ratio." Um, no, you can't do those things, and I'm not going to try to figure out how to accommodate these nonsense choices.