The process is pretty straight forward. For the editor you make a grid of canvas instances, then drag and drop the textures you want onto those instances. When you are ready to save you do a for each on the canvas's, and paste the texture into the canvas, and then get the base64 string, and save that to either one big string with tokenAt(), or use an array.
Then to load the textures, make a grid of tiled background instances, load the array, or string from the editor via the load array action, or from ajax.
You would then parse the array, or sting, with a for each in array, or for n = token count of the string.
Loading it from the string value as the load image from url action.
The string from the editor would be huge however, and you would want to do some optimizations like only saving one texture once.