Dan, friend, I know you will not take it as critique, so I'll try to expose my humble opinion.
I suppose you are using acrilics, right ? So try to mark a little more the shades and the lights. Here in Spain people does it through a method called 'veladuras', something like 'transparency'.
I noticed that is very hard to obtain a good 'veladura', but the Vallejo #596 glaze medium (medium veladuras) can help you.
Mix it with water (20% medium and 80% water), next add JUST a bit of colour (all the stuff must be very thinned, with the same consistency of the water), wet the brush and unload it on a piece of paper (not tissue, just white paper).
Next pass the brush on the area you want to highligth or shadow very gently, the brush must skim the piece and not with the tip, but with the main body (ahhrg! what english! you understand me ?!?).
On the opposite, the Italian school (see Diego Ruina) uses washes. Only wather with JUST a bit of dark colour, wet and unload the brush and pass it on the shadow, putting first the tip of the brush and next the entire brush. The brush must be a bit more loaded in respect to veladuras, and you must wait between a brushstroke and the following (the water must dry to avoid a disaster).
Moreover, as water tends to go down, when appling a wash, you must place the piece in an appropiate pose (to avoid the 'torrent' effect...).
For what I read (and see) Ruina uses the pure black for his washes, but because his tecnique is really different from others (he starts from a very dark base colours, adding layers of lights and using the black wash at the end).
Try it, it's not easy (at least for me...) but amazing, trust me... :lol:
For what I see, you should try using your uniform base colour with Vallejo #921 (uniforme ingles) for shadows and base + #858 (amarillo hielo) for highlights.
Aho!, a capoccione!, don't miss to show me the result!