What is the reference point for how attachable will look on the arms?

When I made armor plates for the legs, I just used the last sprite (where the leg was straight) and sprited the armor to fit. That worked fine but I'm not sure know if the same thing applies to arms because most of the time they're bent holding a gun or something.

Do you want to make an armor covering the entire arm?

I'm not sure if that can be done, but what can be done are shoulder pads.

I was thinking of armor that covered the entire arm, but done in two sections, forearm and bicep pieces, so when the arm bent, you would have the effect of a single piece of armor that's moving with the arm.