First of all, your sprite is nice! Good work. You don't really need the Sega CD Terminator base, you seem to be doing good enough on your own. Please consider the following points, as illustrated by the edit below.
1. The real estate of a single pixel width line at this resolution is frankly, huge. You are for example, illustrating a zipper on the pants. Consider the relative size of that line were the sprite art to be blown up at real size. That zipper would be 5 centimeters thick. Instead consider occluding detail and omitting A LOT more of the lineart. This doesn't mean a zipper needs to be less than a single pixel thick (how would we be able to do this anyway I don't know) but that the line's color can be softer, closer to the back shade so it doesn't scream HI I AM LINEART!
2. Flats and less complicated shades read much better at the resolution, and the pixel shapes ( or 'clusters' if you like my terminology) are much more elegant when not so many different colors are battling for the same spaces. Simplify, simplify. Sadly, this step is not easy to explain or easy to pull off, there needs to be cumulative experience over years of pixelling to explain the choices I made in the edit. If that part of my critique is lacking, I apologize.
3. My version has a smaller palette, which allows me paradoxically more options and more control. I use a lot of subtle tints which which you might or might not like, but just to illustrate the point that they are possible, with a much smaller palette, if you ramp your colors smartly. Investigate in detail in your pixel art program to see the differences.
4. I love my two cats.
