I've been working on a replica Maximus shoulder armour piece from Gladiator:
I made the base shape from cardstock, then fiberglass, body filler and epoxy putty (milliput):
Once the basic form was there, I went back and correct any glaring errors, sanded, then hit the whole thing with hi-build primer and a couple of coats of matt black auto paint.
Here's my current progress:
The shoulder armour really only needs the edge trim added, the leather strapping and silver detailing painted, then it will be finished.
I'm also planning to make the chest armour piece using a similar method, but with a real leather covering, as a joint project with another member here.
I'll try and post some more photos as I/we progress.