My design board is a beautiful, wooden 3 fold room screen. It had cloth panels in it when I bought it, but they were so worn, I removed them and replaced it with flannel. What's nice is that I can spread it out as wide as I like, or just use 1 or 2 panels. It folds up neatly, and like you, I store it behind the door (when it's stored! LOL!) I like to keep nice looking patches on it when I'm not using a specific panel, both as a decoration and to remind me of the blocks I have stored.
However, your wall looks quick and easy and cheap, and certainly looks efficient! If I didn't already have mine, I'd copy yours!