Battle Background Offsets

As of right now, we can't really hack a battle background because you can't place any tiles you create, only modify them.

Excuse my noobness, but what does Zeemis mean by only modify them? You can modify the drawing but not the color? Because, im currently ripping some animation im missing for my project, and since a lot of the animation have transparency, the background are screwing the animation. So, i was wondering if it was doable to put the background completely white?