I'll probably get an angled spare mount in the bed when I bump up to 35s and get a spare. I don't have a full size spare right now. A flat mount takes up too much room, and while I'd love to design a chase rack with a mount built in, I don't know how I feel about blocking my entire rear window. Would look sweet though.
I had mine stood up and strapped to my tool box for a while. I really didn't like how much it blocked my rear window. I recently sold my dirtbike and now have no reason to not run much canopy. I used to run my canopy in the off season then switch out to my tool box and cab guard during riding season. I think I'm going to try to find a way to mount it on the side of the bed standing up.
I think I saw a spare tire mount from JCWhitney where you mount it vertically to the side of the bed. I had one once and I highly recommend if you do get one to mount it to the drivers side so as not to block alot of your view. It would be between the tailgate and the wheel arch.