I think you have the general right idea here. All of the areas of your character are lit from the same angle. You have some cast shadows (such as the shadow the sleeve is casting on the arm, or the shadow the arm is casting on the shirt) and form shadows (such as on the hand and shoe, giving more dimension as the form turns). You seem to be using some hue shifting. You’ve clearly separated each part of the body with use of color and value.
There are some very minor things you could adjust to help give more dimension to certain areas. The shadow you have around the knee area is currently flat at the bottom but you could add a little bit more shadow on the top left of where his calf starts to show that it’s a round/cylindrical form.
You could possibly add a cast shadow from his hand onto his pants; same thing for his shirt, if it’s not tightly tucked into his pants.
The medium color shadow you’ve used on his shirt could be refined a little bit. It’s not completely clear if the shadow by his armpit is a wrinkle (slightly too drastic - could tone it down by a pixel) or the pectoral muscle (too high up if so). It’s not clear if the jagged part of the shadow corresponds to the bottom of his ribcage or if it’s just a fold in the fabric - you could either drop the whole area in shadow to imply a plane change below the ribcage, or just smooth out that part of the shadow to simplify the shape of it.
Implying detail within a small character is a difficult thing to do but I think you’re on the right track.
