Some thoughts: I always thought that Sauron's tactics with the Orcs was basically to overwhelm the enemies with sheer numbers.
Knowing, I would find it odd if they would be well-armored and equipped, so I believe the vast majority of Orcs would be armed with the basics of armor, a basic leather vest with a few decorations. A Orc of higher importance will have more armor, but I doubt they will take it time to paint it fully black. Instead, they will just use stolen armor, and paint a few symbols on it so it turns into a hideous mockery of the once noble armor.

The shock units equipped by Sauron himself would probably have betterarmor andweapons, but I really have a hard time imagining a Orc wearing good quality armor and weapons.

Orcs would also wield axes often, considering that axes are a much more simpler weapon to make than swords.