but what i ment is, for example you have two pictures,
one is 1024x768 and one is 500x800 in size.
right now you would get, depending on the thumbnail size,
something like this:

you can see that the black borders around the second thumbnail are wasting space. they could be cropped away!?

in the thumnail size option you could choose "dynamic thumbnail size"
and enter only a value for the x or y size of the thumbnail...
like i said, would save a LOT of screensace.