A good implementation of the similar Filtering Blocks Demo by Chris. I think it works very well as a gallery.
However, you are using the full size images as thumbnails – forcing browsers to download the full image, and then resize it to 100px square. On final implementation make sure you look at generating some thumbnails to be called for the squares, and then link to full size image. (I apologise if the full size images are temporary, and thumbnails were going to happen any way!)