Looks good so far.
The GoW characters are very bulky and they look like they're carrying half a ton of metal, so i suggest you check out some screenshots for reference. The guy is slightly flat as well as the gun. Try and set your brain into thinking in 3D even when making 2D outlines. Even if you use lineart as a base, it's good to think in volumes rather than lines. Decide the environment colors early on to get the right ambient lighting for the character and fill in the backround as soon as possible but don't start rendering yet.
In pixelart sometimes things get so small that you can't use outline to convey it and each pixel counts, so it would be a good idea to start making edges, shapes and forms with different values rathen than outline.
Looking forward to see progress on this one