These are some nice sprites, I did some edits of a few of them!
First of it's great that you are moving away from black outlines, defining stuff with outlines at this size usually just clutters the sprite. If you look at my edits of the druid and ghoul-like characters you'll see outlines are mostly only used in the lower ''shadowy'' parts of the sprite to suggest shape, while the upper, lighter parts could go outline free. At this size it's crucial to get as much readability out of your sprites as possible, which means playing with contrast of different parts of the sprite.
I also tried to play around with the pixel clusters a bit to simplify and make them mesh together a bit, everything to get them to read better at a glance. Again, nice sprites, these were just some suggestions! 

Hey Cels, lovely stuff as usual!

There's a few things that stood out to me though, and I did a few edits:



1. I feel much of the piece is pretty messy ( understandable considering the scale!) there's a fair bit of pillowshading going on.
One such place where it is most apparent is the hooded villain dude. It looks as if the glowing eyes should be light source, yet every highlight is placed in the middle. Creating a bit of banding.

2. The whole piece seems kind of clean and calm for a war zone, that might be a wholly stylistic choice though. I added some life to the fire, intertwined the flames with the smoke a bit, made the pillar a bit irregular.I would consider maybe adding a couple of gray-ish shades to dirty up the scene a bit, add some details and texture to the ground. Overall I like you palette a lot! reminds me of  Mykola's stuff http://www.pixeljoint.com/p/6661.htm

3. I think the pillowy and blobby shading rears it's head at the portrait again, don't be afraid of angles and creating shapes with contrast, especially when the rest of the piece is all about angles! I don't think the yellow works in the face, it burns a bit compared to the other colors. Places like the ear look pretty rough, plenty of space for cluster optimization there! I also tried merging the colors a bit to get some unity and some of the aforementioned grittyness into the frame.

This is a very cool piece, I have a similar love for that eighties sci-fi aesthetics!
Also I LOVE! the logo that is very beautiful and clever!

Hello everybody! Thanks a lot for all the input! and sorry for my late response!

@Ambivorous: I intend to keep the rock spherical indeed as that was part of my initial concept of these floating island planets!
I see the sense in having the clouds frame the picture, but I don't really want to make everything spherical in that way. I'll try to think about how I arrange the clouds though!

@EvilEye: all fair points that I agree with! I'm actually unsure whether to even include the blue afterglow in the first place I don't think the piece really needs it. It sort of works against the simplicity, or maybe it could be done in a more delicate manner.

@Drazelic: also a fair point! And why I in my initial post said  I was the most unsure about the leaves. I have a few different styles of rendering going on there at the moment and I'm not really a fan of either. What I'm aiming for is something light and cartoonish while still maintaining detail. There is a KennethFejer-esque quality to the piece I'd like to keep. Edits on the leaves would be very appreciated!

I'll update this as soon as time allows, as I said I've been doing this between pixelling for work...and right now work has taken precedence,

Hey Cels! kudos on taking the piece as far as you already have! Hard work pays of!

I messed around with an edit earlier today looking at it now it might look a bit muted.
What I mainly did was upping the contrast creating some difference between light and dark for this menacing character.
I also tried to tie your ramps together a bit. I would even consider incorporating more red-ish shades into the skin tones to  separate them from the gold. I also took a stab at trying to fit the helmet after your reference, but if you're deviating from it that might not matter much!
I do think the blue tufts of hair read a bit as blue flame, I think more muted colors/removing the highlight might help here.
I messed around a bit with the codpiece skull and gave it a stronger shadow. You have some banding to look out for (for instance on the skull on his right leg around the eyes).
I realize scratches and other such details is something you'll add later on but I messed around with it anyway
Also I'm not a huge fan of the excessive reflections on the gold trimmings, I think a simpler approach is easier on the eyes and won't clash as much with the red part of the armor.

It's already an impressive piece, and I'm excited to see where it will end up done :3