ugh I typed a whole paragraph and then the page refreshed and I lost my words. Basically what I wrote was that your art work is too messy and looks like Oekaki as does most of your art in your profile. Check out this website if you're interested in learning more pixel art skills.
- Your 1 point perspective is wrong, your vanishing points are all over the place and are not very convincing
- You're not respecting your own horizon
- The chipset texture is not very good, try using just right angles
- You're not following your curves, it should count like 4,3,2,1,1,1,1,2,3,4. But it doesn't.
- Jaggies, Jaggies and more Jaggies
- Your outlining is very inconsistant
- Your art work is full of orphan pixels
Please don't feel discouraged, I only say all of this to help you so that more of your work can be approved and shown in the gallery. 
Thank you, I'll try my best.