oh look.. its yoshi...
simple but effective 4 tone shading, i feel that the spikes on the back are different base colours... or just shaded wrongly... also try to keep the light source in the same place.. as most of the shading shows its top right... but there are areas *like the tail* which say bottom right... just a point... very animation styled... not bad... but just need to keep the areas of your shading in mind...