You need to limitate the number of colors of your pallete (by what I can see, you need like 5 shades of red, 1 of black, 1 of white, 2 of purple, 1 of yellow and 2 [not 50] shades of gray).
Try to posterize it, after that retouch it under the same pallete until it looks as good as you want. Finally you can try to make transparent the background color if you want (Not semi-transparent because isn't alowwed by the rules).
Check out some user's galleries, analyze the pixel art and you can upload the yours shortly.
Gud luk
Very true. I am still learning. Thank you very much for your feedback. I think it looks pixelated/image because I do not understand how to make curves without it looking boxy. So it's blended, not pixeled. Maybe I should increase the size (number of pixels)?
Nice work, but I don't think that this piece is pixel art, I only see a very pixelated picture
Sweet! That helps a ton! I really appreciate your advice and feedback!