[Zubersoft]

Assuming I'm not misunderstanding you, this feature is already available. If you load your setlist, then bring up the setlist popup window, you can just tap the add button (plus symbol at the bottom right) to add a song temporarily to the setlist. You can save that change by tapping the save button.

The other option is just to go to the setlist editor and add the new song... I'm not sure what you mean by displaying the name of the song versus images/pdf. The name is always displayed. I don't think images/pdfs are shown anywhere except in the song editor.