This is such a staple that I'm in doubt whether I'm not missing something here. :)
In the image editor when resizing a picture you can only input width and height separately.
It would be really useful to have:
a) a 'maintain aspect ratio' box
b) choice to resize by specifying dimensions or percentage of the original
Curretly when I need to resize a graphic in the sprite I have to use a calculator. :)