Well, welcome to the world of pixel art! There's a few things wrong with this piece that are holding this piece back
1. The sword and shield are too similar in color to the main body that it's kind of hard to read.
2. You need to work on the anatomy. I like the look your trying to go for, but the body is a box, the legs and arms are too thin, and there is no neck whatsoever. (Not trying to be mean or anything so sorry, I suck at anatomy too so I'm just spitting out what others would say to me)
3. I would recommend making all of the objects basic flat colors like you would see in a cartoon that it's easier to work on shading. After that, you can add in all the details for the sword and shield, and the cape.
I'm kind of new to pixel art myself so hopefully someone more skilled than I am can help you out with this. Also, since I'm new, kind of take my words with a grain of salt.