That reminds me of those Oblivion Lords in Elder Scrolls IV. Very cool!
Only problem I see is that I think the face on the maskless one is a liiittle too hard to discern, and that the red plating needs more contrast. I think reduce the number of dark colors in your palette by one and then add a very bright color for the shine coming off the armor(?).
I opened it on my comp to look closer and it's definitely got some pillow shading. Find a light source and then add shading beneath folds. I recommend discerning a light source (such as upper-left) and then use that light source for everything. Even if the light source on the map isn't coming from the direction, the sprites will still look way better than if all light comes from above their heads.
Nice work so far