The status bar, background images, wallpaper and dock pages work the same way with regard to image handling. They differ only in the portions of the screen that are affected.
Please refer to the Overview to learn more.
The status bar is the background for the top strip on the phone screen. It is normally 320 pixels wide and 20 pixels high.
It covers the movie, wallpaper, slideshow, and background images. There are several versions on the phone; WinterBoard replaces only the black version that is used by the Home Screen, Weather.app and Stocks.app for example.
Since you can easily integrate the status bar into the wallpaper or background images (different status bar on each page,) it is more convenient to just make it invisible (suppress it.)
To change the other status bars, you will have to edit them directly in the File Manager (if you can find them.) The one used on the Lock Screen, for example, is .../SpringBoard.app/FST_BG.png.
A double-click in the work area will make a snapshot of the current status bar and save it to the wallpaper images folder.
Note that reverting does not restore a list of assigned images (that is, the 'work in progress') but instead adds the StatusBar.png file (if present) to the list of assigned images.