Dobrescu George
Reviewer: AudiophileHeaven
I wouldn't know about the X5, but you're right: I completely overlooked buttom_bg.png thinking it pertained to buttons.
Glad it worked!
We had a thing going on with the first X5 and X5ii, where a few of us spent some time making themes, if the same rules apply to X3, the theme is highly customizable if you have the time to work on it

Even though the resolutions won't match, you can check X5 FW threads as he examples in there are very useful on how we did some things when we made a few themes for it.