Even better would be to show all 3 thumbnails the same size...but that might be being greedy.
Not just that, but have the thumbnail actually be the same as the full size image (but smaller), not just a cropped version of the upper left corner.
Example, Cypress: https://www.wincustomize.com/skins.aspx?skinid=7116&libid=1
Look at the bottom 2 thumbs, what the heck is that supposed to be? The first thumb there's nothing shown at all, and the second one you can *barely* see the top of a window, that is until you click on it to see the full size shot.
Does it on the home page and main gallery page too. It doesn't matter once the other site goes live...although the right side of all those thumbnails are cut off too. 