Zolxe said:
How about larger thumbnails...

...I have written a short javascript file [...] which simply resizes the appropriate elements.

Anyway, I just thought I ought to suggest it since I thought it would be a good improvement for the site...
This feature is already implemented. As I said, hold down SHIFT and point the mouse cursor at a thumbnail.

You can also scroll a large image post by click-dragging as well.