I'm actually doing this for my current main project, which is a vertical scrolling SHMUP for mobile. The way I have my project setup, is I have two separate background sprites that alternate randomly("Background1", and "Background2"). Each of these sprites, have multiple animation frames(three in total with "Loop" turned off). Screenshot Here
Then in the GameSettings Event Sheet that runs during the main Layout for the gameplay, I have a Global Variable named "Background", which is a number. Each time the Play Button on my Title screen is clicked, I have a group of Events in the same GameSettings Event Sheet, to control the background frame it chooses for that play through. It looks like this
So the player will see one of three of the backgrounds, which alternates between two separate sprite objects by placing one in the Game Layout's Viewport, and the other directly above it so they are touching. Then they just move down the screen by 5 in the Every tick Event/Actions.
Not sure if this helps it all. It sounds like you've already found your own method, which looks like it would definitely do the trick. This is just another method to accomplish basically the same thing.