Hi @747marine Welcome to GM Authority!
To answer your question: it’s not possible to change the background of the display. However, you should be able to change the “theme” that changes the general color scheme of the display.
Also, regarding the storing of phone numbers: yes, the OnStar system can locally store 30 names/numbers. But if you are pairing your phone via Bluetooth, then it will synchronize the names/numbers from your phone.
Does that help?
