The picture should still be displayed in the background when the adjust picture menu is on the screen. Depending on the route your using to get there, the screens are a little different.
Try using the arrow buttons on the remote while viewing. The screen will allow you to adjust dish position or skew (if not fitted with a voltage controlled LNBF). Just a banner will appear on the top of the screen with the info.
The options in the menu for picture adjustment also contain the quality reading on a digital channel. The menus are different on analog channels 1-24.
As far as modern TVs, when I tune to a non-existant analog channel that is just noise on my 922, my TV displays "check signal cable" and goes to a black screen in a few seconds. It hate that. It makes for fun tweaking a dish.