I tried my hand at simple miniature customising today, with a headswap on some stormtroopers. I had an old bespin guard, and some clone wars figure, that I never use, so I took their heads, and turned them into Rebel Spies for my Imperial Starbase scenarios.
I'm making a solitaire mini game, where stormtroopers randomly patrol to waypoint markers placed on the map. One or Two spies (depending on scenario) must do things like download data from computers, shut down shield defence, rescue prisoners, and stuff like that. I'll make a dozen or so custom 'spy' stat cards, that have different stats, skills and abilities. Then a mission is picked, and the selected spy can try to carry it out! If a stormtrooper gets too close to them, a roll is made to see if the disguise is seen through, and there's possible combat, or things like stormies running to set off alarms, etc.
I made a generic sci-fi spy game along these lines a couple of years ago, and plan to take those rules and expand upon them, into a star wars miniatures adventure game :)
Anyway, here's a pic of my two spies in stormtrooper armour.