I need a tool that allows me to edit the alpha channel in a RGB PNG like a bitmap (I need to lay pixel-art-level partial transparencies over a pixel-art piece, to make some glass effects)

I know that I've done it a long, long time ago, but can't remember what tool did I use. Do you know of any?

Well, this is much more stylish but, know what?

It doesnt' satisfy me AT ALL  Besides the exercise and the lighting *pattern*

It doesn't feel physical at all. I don't know how the heck I'm going to add any details to it. It was fun doing it but it just feels wrong somehow.

I'm going to take the pose and lighting from this version and try to give it a finish closer to that of the first one.

It's not like I'm making it pillow-shaded on purpose! X_D

Thanks for the tips, already tweaked the palette.

Now I'm going to remake the girl with reference from Posemaniacs and proper lighting.

Well,not right now, when I've had lunch
%D

Had lunch. Going to rework the girl.

Thanks guy, no offense taken. When I said the face is almost done, I wasn't thinking about the eyes and the nose, I'll work one those. The eyes in particular need to be softened, darkened, and re-sized some. The colors aren't off though, the palette is taken from the photo itself, I want to make it have a more yellowish tint but I think it just looks off because the hair isn't colored in yet. Ill post an update soon.
Oh btw, Lightning's a girl... Maybe the chin need's to be softened and re-sized.

Yes, if you squint your eyes really hard, you'll notice the lines between her chin and cheekbones curve outwards in the original while in your version they curve inwards. And the chin itself protrudes too much in your version.

I also think that it'd be better that you used varying colors for the outline. Well, now I'm noticing it already has black and brown outlines, but I mean several colors on the same line.

Sent you an e-mail a few hours ago.