Tip: When making your overworld, mix the terrain up! Add decorations to the overworld. Don't leave large empty grass or sea regions. As an example, angled land and multiple colors look much more interesting than square land and flat, plain colors.
Snow land created for your hacks. Give me a credit :3
I'll have to reject this graphic, because not only it breaks one of the Core Values, but because it could be a lot better.
First thing is the shading. It's lacking shading in the dirt part of the ground, which make it look flat. The grass suffer from the same problem too. About adding shades, I recommend getting a tutorial about light sources and shading in pixel art.
Second, it break the Core Value about simple edits. Make sure your graphics are made from zero or at least, that is a simple edit that may be useful for everyone (like the midway animation fix we have hosted here in the site).