access to the textures within GUIStyles?

I would like to do something like what can be found on the bottom of this page:

That is, I want to create GUI elements that use the dimensions of images I import. Is there some way to grab the images from a GUIStyle? Say, make the dimensions of a button’s Hover state match the dimensions of the image I drag onto it in the inspector?

And if so, where can I look up how to access this kind of property?

Got it.

Awesome.