The head:
Fist of all, the shading looks bad. It is shaded like this:
Now, look closely to the girl in the last pic you made, there are no round circles but it follows the structure of the head a little.
You are trying to get a cute anime head, right?
If so:
-get rid of the nose
-make the eyes MUCH bigger
-open the mouth.
If not:
Go search for some photos or search for head anatomy on google and look at how a human head is built.
I would start with working out these things and after that you can move on in the progress of improving your pieces
The egg(?):
This looks like it has no effort put into it at all. You should working harder on this.
The iso building:
It’s very basic, but it’s good to start that way.
You have a problem with your lines that makes it look unrealistic.
Lines should be:
Yours:
(click on them to zoom)
I recommend you to this:
http://rhysd.syntesis.org/tutorial/And you should also check some other peoples works and learn from that. Watch the color of their lines closely.
The room:
This looks like a collection of non pixel art to me. The shadings aren’t drawn by hand so you should change that.
You also got the same problem with the lines as the iso building.
Well, I hope I helped a little
Good luck with improving