Well, some commercial modules have incorporated TimThumb rather messily into Zen. It obviously works but would need to be thought of a bit more.

I am kind of interested in that in my on-going exploration of what the best way of dealing with images is :-) Which Diva knows all about.

The advantage of TimThumb is that it is pretty actively developed because of it's use in a lot of wordpress themes. And it is powerful. Perhaps too powerful in some respects. But it is a very solid bit of coding that actually would not be all that hard to incorporate into Zen in a nice way.