How to remove category widget image or shorten the image?

Today I added images to the category which looks great in the category page. But the same large image is also showing in the category widget which is looking odd in the widget, also because of the image above the category name the category widget is stretched too long down to the bottom.

So I want either to remove images from the category widget or shorten it to fit side to it just like what it was when images were not added(to the size of folder icon when images were not added).

What to do? Please help!