You've come so far in your artistic journey that I can easily mistake this for official art.
I would have definitely bought a poster of this back when I was watching the show all the time as a little kid. :P
Great work with the all the details and attention to light sources, I can easily picture movement from them as a result of the anatomically correct muscles and bones. Someone definitely did their research before getting started.
The only thing I think that could be improved is the bottom row of teeth on Greymon and MetalGreymon. With the current shading the teeth look a little bit too thin. Rounding it out with a thin shadow of some extra light should give it the 3D look the rest of their teeth have. Perhaps even changing the bottom of the tooth to be rounder could work as well. However, I'm not the foremost expert on lighting, so take my advice with a bag of salt.
You're doing great and you've still got plenty of potential. Keep it up Boco!
P.S I dig that 'Hell ya!" expression all of them share. :P