The wall paper appears only when I start the car and do not press the ok button on the nav screen.
Once I hit the OK button the screen be it cell phone, audio it stays on. Is there any way to activate wall paper if the screen remains inactive for a while?

 

Not that I'm aware of. You can go back under the menu screen and view the wallpaper to turn it on again (Theres a little button that stays up that says "press ok to exit" when you view it this way).

 

There isn't a way to get your custom wallpaper to show up after a period of inactivity like a screensaver. However, you can manually do. Press the Info button, toggle to the next tab called "Other", and scroll down and click on "Show Wallpaper".

Now your wallpaper is active even after you have already hit OK at vehicle startup. Not exactly what you're looking for, but somewhat closer to your end goal. Hope this helps.

 

Interestingly, however, it won't let you do this while vehicle is in motion. I say "interestingly", because it will let you navigate through the options, but when you finally get to "Show Wallpaper", that's when it stops you (giving the "tut tut...not while in motion" warning). Why it lets you be distracted by going through the options menus, but then puts the brakes on actually showing the wallpaper, I'll never understand.