Definitely post it! There are many skilled people and several professionals regularly posting here but it's useful to upload regularly to stay motivated and get feedback. Everyone's on their own path to improve, whether they are amateurs or professionals. 

Wow, someone actually commented. Thanks for the advice. I actually have some better works (I think), but they are kinda average in comparison to those that people usually post here. Do you think I should upload them?

Nice first submission! The proportions seem a bit squished compared to how he's usually drawn but you did a good job with the metal reflections. You might want to try to put bigger areas (clusters) of bright pixels rather than only thin lines, especially when there's so much contrast.