making it transparent now will give us a better idea of what it looks like on a mid tone background. white backgrounds are horrible for viewing.
te sprite is simple, there's no doubt about that, but maybe too simple. if you're going to go into enough detail to put lighting all over this leg, you might want to do the same to everything else.
you have very little contrast to even tell that the front of his face is lit up.
the muzzle flash looks more like it spurting out yellow goop. try adding reds and oranges to it.
also, go through some steps when drawing.
my first step is always a work station:
create a color palette (even if it's temporary, you can always change it)
and give yourself some room to work with. your sprite in enclosed in a very confined area, which, in most cases, people believe that they need to stay within that area.
staying inside a small area will keep your ideas limited and, to me, puts pressure on what I'm trying to draw.
now, looking at that work station above, notice how similar a lot of those colors are.
you have very little contrast, so it's going to be very hard to tell the difference from one shade to the next, or if his arms overlap eachother, it's just going to look like they're melded together into an x of arms.
change your colors to grayscale with a function, don't go and change everything to a gray. changing your colors to a grayscale will really tell you if your contrast is working like it should.
a lot of these grays are close to the same, so what you do, is shade by the brightness of your color, then when the brightness is good, go ahead and fill it in with some color.
this isn't always needed though. when you get better and you can really understand the brightness on colors themselves, instead of grayscale, you'll have no problem shading the way you should.
here's my edit. check out how many colors I used compared to yours. when you can use the same color somewhere else, do. sometimes you'll be stuck with using a palette for an entire game, so practicing with limited colors will do wonders.
welcome to pixelation and good luck.