Thumbnails in 2.5

2.5 seems a very good update, but I’m a little troubled by the thumbnails.

In previous versions, they seemed to be of fixed width and variable height, so that readers could see the whole image. Now in 2.5, however, they’re a fixed shape, and parts of the image are often missing, which makes them look strange and possibly ininviting.

Is there a tweak that would allow me to go to something like the old arrangement in respect to thumbnail format please?

Thanks,

Gav