A unique style, haven't seen one like it before!

Peeter: that's about just what I said, right? XD

Pukahuna: better!

That's a weird way to hold a torch, so close to one's face. That's why I thought candle.
Anyway, still needs more shadows on and around the torch stick. 1, 2.
Also the forearm would cast a long shadow down the lower torso and thigh.

There are a lot of different themes on pixeljoint with different background so in some cases transparent bg doesn't work at all because then you wouldn't have any control over what your piece looks like. If it's meant to be on different backgrounds (like a game character) it would work, but transparent bg would break a piece made for a specific background color. 

 This is an amazing piece as well! I love how you shaded this guy and the colors you used..

 the colors are a bit overdramatic but otherwise very nice

just needs a different colour for the BG. like a really dark navy or something.

 I improved the contrast, the horns and legs, looks better?

I loved it, insta favorited! Love the concept of the character and the colours, it would be nice to see a game with those kind of characters.

 Thanks for the tips :D, the main light source is the torch, but the whole armor and sword has bright parts, I did not use any reference for this, neither to anatomy nor for the colors, I'll try to improve the things of you pointed out, sorry for my bad english

It's not a rule, and it's not about solid bgs, it's about useless (=lazy) bgs. Usually white and sticking to the sprite edges, when transparent would look better. No prob here of course, esp since the dark bg enhances the colors.

Looks good, but many directions remain for improves ;)

Needs more contrast. Maybe way more, depending on the light source!
Is that a flame next to his face? Is it the main light source? Is it a candle he holds in his hands? Is the sword hilt area glowing too? Other areas?
These questions have no obvious answers right now, but they would with proper shadows and contrast.

Body and pose are very unnaturally rigid. Did you use a ref for anatomy / pose? You should!

Some shapes are jaggy and need refining, esp his left leg (our right).

Perspective of the helmet horns is off: his face is turned slightly to our right, helmet top looks turned to the opposite side because of the way the horns attach.

Nice colors, but as a whole many of them share similar values. Again, contrast!

 It's reccomended against, but there are cases where solid backgrounds are allowed. Here, he has external AA, so it's okay.

It'd be nice if it was an oval instead of a rectangle though. Y'know, at least put some shape into it?

This pixel art is not for any challenge, so I think there rules about transparency, because I've seen / posted many pixel arts with solid color background, I also can't remove the background because that has external A.A 

I believe there's something in the submission rules about no solid color backgrounds? Just make it transparent. I could be wrong though.