Going off from what eishiya said, definitely make sure to re-use colors when possible, I myself used to make pixel art with an absurdely large amount of colors but I later started fixing that. The pixel design and drawing is quite fantastic though, and the red light coming from Kylo Ren's lightsaber is a really nice touch.

Thank you for the feedback. I'll make some adjustments for any future artwork I may post.

The drawing itself looks good, but you're using a huge number of colours compared to how many you actually need. This piece has 81 colours, but you shouldn't need more than 16 or so to convey the different materials, shadows, and even the red reflections. In pixel art, it's better to reuse colours you already have than to pick new ones, because it makes it easier to adjust things later, and keeps things looking unified.

Also, your thumbnail is NPA (non-pixel art), because it's automatically resized. If you need to make a preview image from a larger piece, it's better to crop than to resize, so that your pixel work is preserved.