I just took the plunge to Mint 20.3 (Cinnamon) and once again, the "dueling background images" has reared its ugly head - again!
I picked a background image. Used it a few times. Restarted the laptop a few times. All good.
I then decided to try another background image. Restarted the laptop, but now, the original image appears first, albeit very briefly, followed by my new background image.
What going on here? Any clues, guys? It's very annoying.