When editing background images, they are similar to visemes except for their appearance, which are in the form of flags and not boxes.
Point the cursor on a background image and it will turn into a hand. Click it twice to call up the editing dialog box (go to #2) or once and right click on it to Edit, Delete, or Remove All.
If you choose Edit, a dialog box will appear. After you have finished your selection, click OK.
You may also go through the menu HAP > Edit Selected > Action > Image after selecting it. Select another image and then click OK.