This is a project I created to create levels. My goal is to program a jump and run in Flutter, without a game engine. But to create levels I needed a level editor. This is this project, you can upload your images in the editor. Then you can place them in your level. You can give certain tags to the parts to find them later in your program. When the level is created you can save it as a .json file, and then load it in your project.

I would like to create a package on pub.dev which will load the level for you. You would then only have to implement movement and collusions, which is easy since the loaded data contains the positions of the tiles. For more details, I recommend to read the tutorial.