[WIP] My first pixel art ever.

[Jim16]

That backgrounds looking really good, you sure this is your first Pixel art  Also, moon over the moon?

So, as I thought, the basic tile you have there has a lot of noise. Thats not necessarily a problem, but I'm sure there are better ways of doing it. Go look for gameboy examples and have a look at their tiles. Don't rip though, it's frowned upon. If all fails just keep with what you have. It might also be an idea to look at "real" life astronaut suits, you might pick something up that will make your character look just that little bit better. Just don't try to cram in small details, it won't work at this size.

The character stands out perfectly, so I see no problems with it.

You seem to have a problem with AA, here's a simple tutorial by Derek Yu that puts it so simply. Simple enough for me to understand 
http://www.derekyu.com/?page_id=228

Getting back to the contrast issue. Maybe not an issue to you, but its really bugging me. So I made an example to perhaps sway your mind.
So this is the original:

Up the contrast:

lower the brigtness:


Your pallet just doesn't seem true to gameboy. I know the contrast is huge on the gameboy, mainly because of the crappy screens which made the colours seem dull and depleted. They probably could of done with a back light back then  What I'm trying to get at is that your pallet could be somebody's interpretation of what they saw. Which is totally wrong and not accurate! There is no correct pallet out there as far as I know? Somebody correct me if I'm wrong, but its good to try and get as close. Hope that helps.

[Toyoto]

It's not the Moon, it's Mercury http://www.wwu.edu/depts/skywise/planets/mercury.jpg and that moon should be the sun, though should be bigger due the distance Mercury is. The background isn't pixel art. At least I didn't make it as pixel art should be done as I've read here. It's a handmade drawing then posterized and retouched by hand. I didn't do it pixel by pixel.
No idea about the exact palette of the Game Boy. In magazine screenshots the colours often varies depending the way the screenshot was taken. In many the colours look similar to that. Though in real life everything was much more green.

The game doesn't pretend to be realistic at all. Besides that I don't know how to put more detail in such a small size.
I read that tutorial before starting but could you be more specific about AA? I mean, due the limitations I'm working with, I don't know how to do it better.
The colour palette it's not a problem. I'm just working with I've been asked to. Pretty easy to switch colours. My real problem is not quality but quantity