[3.0.3.7] change category thumbnail size

How can I change the size of the image at the top of a category listing?

You can find it in
In OCAdmin > extensions > Theme > images > category image size - set at 80x80 as standard.
Max size is around only 120x120 though with this method.
The image size is fixed by the <div> containing it

Can we change the div size? The thumbnails are so small even on a large monitor they just look silly