Extremely well rendered piece of pixel art, I love it.

One thing though. I suggest swapping the lightest grey with blue. Makes the palette much more vivid

See how well it counters the red and makes for a interesting shadow on the trooper.

Very good pixel tech!

This is amazing. Awesome details and reflections.

The only thing that bothers me is the position and size of the two circular highlights on Vader's visor.

They look like cartoony pupils and make him look somewhat cross-eyed and goofy.

It might be a better idea to make them more subtle similar to the stromtrooper's visor.

The red reflections on the left helmet look good, especially where the edges are accentuated by highlights. The right looks a bit off by comparison though. I would expect more angles to reflect the red light if the helmet's material was "shiny" (like on the vader helmet). But any less reflective than that and I would expect the glow to be a lot more diffuse. To me atm it seems half way between.. thought it was red paint at first for a second. 

Looks good to me aside from that though, good work fleshing out the weird shapes and curves of these helmets convincingly.

Thank you, Manupix! When I have the time, I'll try to take your advice and update it :) That example image already helped me a lot in understanding how the red light should shine on the helmets.

Great pixeling as usual =)

About the light: depends on other light sources. Atm it reads like the 'force light' adds little light to either side of the scene, both being lit by strong diffuse white light from the left, reflected from the right.
Speculars aren't too realistic: as Vader's helmet is glossy black, the lightning should reflect almost as bright (visually) as the source; and you could not see any reflection on the trooper's (except in the dark parts) since it's already pure white.

You might have lit the right half from the right with the main white source, and have the red light only (or mostly) lighting up the left side: everywhere not a specular should be red, and speculars white. Poor example here.
Also speculars love edges, the sharper the better!

I'd saturate those reds somewhat more, and maybe shift them towards purple a bit, as they are nearly pure red hues.