My shelf mostly consists of Fighter Pods and Heroclix with some popular culture Hot Wheels. Fighter Pods and Heroclix have a wide character selection which cover multiple licenses. You can have Batman and Spider-man or Captain Kirk and Captain America all in the same scale and style. Plus, they are inexpensive and small, so they are easy on both the wallet and the storage space. As far as the Hot Wheels go, who can resist a Batmobile or the Starship Enterprise for $1? Apparently not me.
I also customize both Fighter Pods and Heroclix and will be posting these as well.