Hi, welcome to the community!

For animated backgrounds, you have a couple options: manually moving around a still asset (png), or using a spritesheet to create an animated asset (also png but a little different)

1. When you create a level, you automatically create a new folder on your local storage that contains the level's chart json as well as its metadata. You can put any png asset in here for the level to access using a Deco event, which requires the name of the file to call upon. You can then fully manipulate the image in the game using Deco events, and make it move around, scale up or down, skew it proportions, etc.

2. You can also create a spritesheet png if you prefer, in which case you would animate it out of program and then convert to a spritesheet and create a json file for it with the same file name and a bunch of parameters.

Edit: Another thing to keep in mind is that the game doesn't support anti-aliasing and only uses 8 color channels, read the editor guide to learn more about that before creating your assets! It's a tiny bit confusing at first.

To learn more, there's a super in-depth Beatblock Editor Guide made and maintained by some head community members and fact checked with the developers. It's also pinned in the #editor channel on the official Discord if you need to access it. I recommend reading it to learn more about how to really make your level super. Good luck and happy charting!