I live in a rental property that has a tiny yard out back. I’d love to paint it just to brighten it up a little more for sitting out in the 3 days of UK sun, but don’t want the landlord to take a hissy fit and steal my deposit. So if I did paint it, is there a (easy) way to strip it before I leave? 
You could get some pretty thin sheet rock or maybe play wood, lay them on the ground on some cheap painters plastic sheeting then paint a mural or whatever you want, then when dry you could mount it directly to the wall. Just unscrew it when you leave and voila.