Wall mural - what to mount it on?!

Aunty-Pickle

Help and advice needed please! And apologies that I can't explain it very well - it's all imagined in my head and I can't even explain it to my OH!!!!

So, I am making a Noah's Ark 3D kind of wall mural thing. Fabric background, wooden ark, toy animals, foam tubing bits for rainbow (covered in fabric etc) etc etc

My question is, what would be best to mount it on so it can then be hung on the wall for LO to play with?

I had originally thought of sewing it all onto an old duvet (which could then hang on the wall from a pole if I do like a border with eyelets) but I don't know if that's too bulky?
My other thought was sewing it all onto a sheet which is then mounted onto a piece of plywood (or similar)

Any comments/suggestions/advice?