I think a great way to make the Ewoks more fierce seeming would be the simple addition of a shot of a pile of empty, broken Stormtrooper armor, that Han looks over and sees as he's hanging upside down about to be cooked. It implies the Ewoks have been killing Imperials for a while, and makes them scarier.

Say I could score a few armor suits, and perhaps made a set of some sort to match the Ewok village.

How could I film these, and have that image be anywhere near the necessary quality to be seeminglessly inserted into ROTJ? I'm just a simple man.