Welcome to the forum SeventhBus
I'm currently seriously enjoying the first part of that link, so thanks for that.
If I separate 'image' from 'background':
Assuming that you mean 'albumart' when you mention 'image', it shouldn't be difficult to have all these tracks displaying that same mage.
You could e.g.:
Embed the same image into the files.
Place all files into the same folder, tag all the songs with the same 'album' and 'album artist', and add some cover.jpg to that folder
This will all depend on you have setup: Tags (1) > artwork
I'm sure there are other solutions and more useful explanations, which shouldn't be hard to find doing a forum search on the matter.
That indeed sounds like something that could be achieved using a Theater Mode.
It would have to be created, or an existing one would need to be edited.