I can see subtle hints of shading. Takes a lot of squinting to see it. Perhaps make it more obvious or something. Take a look at the SRB2 official sprites. You can clearly see that they have shading, correct? Don't make it so it's too dark, but actually have some kind of obvious shading. Take a look at all of the good character wads, even. They all have a real obvious shading, you don't have to strain yourself to just notice it.