I used the HGSS Silver Overworlds as a reference and the base was from a R/S/E Red Trainer overworld. I left the eyes the way they were because I leave the eyes alone when I edit overworld sprites, also the massive hair was because of two reasons. One was the SIlver HGSS reference, and Two was that Silver's hair is kinda like a poofy spout of hair that drops down the sides of his head, though it does look like he has a rather massive forehead.
Leaving the eyes alone is all well and good, but not if it's based on a different style to the other overworlds- in this case, it is. My advice is to never use an RSE overworld as a working base- they're horrible, in comparison to the other styles.
Regardless of whether you like it or not, Nintendork- mixing overworld styles is a no-no. It just looks bad.
Anyway, as I should have mentioned before... You need to work on the mapping. They are far too cramped, generally- they also use the small tree as a border and such, which... Well, it should never be done in a map. I know that in GSC it looks like they did this, but that's just because they didn't have a big tree/the slender trees were considered as the big trees of the game. Look at every game after GSC- the maps all use the big tree as a border. It looks better, frankly.
So, my advice to you is... Practice mapping. ALOT. Reading a tutorial is fine, but you can't learn creativity from someone else. Having said that, you can examine the various other maps in the games, and practice different methods you see. But definately, work on the maps- start off by making them MUCH bigger.