Here's an attempt to help you with some of the issues you're having.

Some explanations / thoughts:
- At this small scale, you need to be really careful about adding detail. Less is more. The clockwork inside the robot could read as anything, like flames inside a stove, or a golden cloud, or small fans / windmills. Make the cogs bigger, so they're easy to identify. Maybe the scale of the clockwork is not what you had in mind, but it's easier for the eye to identify. You're basically drawing a cartoon version of your concept, at this scale. If it's not easy to identify, leave it out of the sprite.
- I've made some significant changes to your color ramp. Instead of 4 disconnected ramps, I've tried to connect them a bit. At this size, the difference between a dark brown and dark grey-blue is almost impossible to spot. I've also tried to vary the hue within each ramp, as the wood moves from a cold colour (purple-brown) to a warmer colour (golden brown), for example. The metal isn't just dull grey, it goes from a grey-blue to a grey-cyan (from cold to warm).
- I've used different colours for the outlines, so to reduce noisy contrast a bit. The darkest colour is for outlines used on the dark sides, and brighter colours do the same on the bright side.
- I've tried to get rid of as many individual pixels as possible, as they often add noise instead of contributing to the piece. Notice the tumb, for example. In my eyes, it's just a single white pixel with no purpose.
- I've tried to do a chrome effect on the metal helmet, so the reflection bounces from bright, to dark, bright again and then dark. You can just go from bright to dark to reduce noise, which will make the metal look less polished.
- It's hard to understand how your model will actually move, mechanically, when the thighs seem to be cut from the same piece of wood as the torso. So I've added some lines to separate the thighs.
- Please do not use dithering to simulate wood on this piece. It just adds noise, contributes nothing. I agree that vertical lines are the way to go, but I've tried to use slightly bigger clusters, so it doesn't just look striped.
- Probably some other stuff I've forgot to mention.
- What's the weapon he's holding? It's a bit hard to see. Could be a gun, a chainsaw or a leafblower

If it's a gun, maybe he could hold it a bit more aggressively or in a way that makes it easier to recognise as a firearm.