There are five buttons to the right of the picture list:

The Set button is only enabled if exactly one picture is selected. Pressing this button causes the selected picture to become choosen, i.e. this picture will show up at next startup. If the picture was disabled, it is automatically enabled with a weight of five.

The On and Off buttons enable respectively disable all selected pictures. On enabling the weight will be set to five.

The New button creates a new list entry. If there is a picture on the clipboard, it is used. Otherwise a default picture will appear. The picture is untitled and disabled, but will be automatically selected. This featurewas added primarily to provide a way to import a picture from the clipboard.

Last but not least there is a Delete button. It (guess what…) deletes ALL the selected pictures. This operation cannot be undone and the pictures are permanently lost.