Hi Diamphotoxin,
There are a couple aspects you can improve on the shield:
- The first one is highly subjective but I would avoid connecting pixels at the outline in a staircase manner. Some people do see diagonals as disconnected pixels so this is merely personal preference.
- The skull hardly look as a skull, always reference pictures if you can. No matter how much experience we have as artists is better to never trust memory.
- Always have in mind the lightsource and how it interacts with the object you are drawing, this is the key to make something look good.
- Study reflective materials, they have a pretty specific behavior. I recently explained it so please check this post
https://pixelation.org/index.php?topic=65186.msg257285#msg257285I do not have enough time for a full edit so I re interpreted the skull, the ornament on top of it and the corner at the bottom as a standalone thing. Hope it helps a bit to illustrate my point.

PD: Use imgur as an image host to post on the forums as .png, avoid inserting images as attachments since it takes really long to be approved.