the remote isn't really designed to work with custom graphics.  if you search for the MX880 graphics thread in this forum you can apply the same methods to play with the graphics of the MX780.

I played around with it a bit, but since the screen isn't really up to the task, it seemed like a waste of time and I didn't feel like I really improved upon the original graphics. (At least as far as being able to easily read the buttons is concerned)

I would suggest upgrading to a different remote if you really want to play around with graphics.