There's really ont much to crit until you start shading, but right off the bat, I notice that you have really dark outlines in some places and black ones in others. I suggest giving the foreground stuff such as enemies and the character outlines or extra contrast and placing less emphasis on the other areas, such as tiles. Also, decrease the saturation of your art. Right now it looks like crazy neon all over. Tone the colors down and give the lines some more organic forms to make things look mpore natural.