I was going to suggest ConceptArt.org but I scrolled through a sketchbook and found a post by you.
I don't know if this is the "art-themed message board" but listen to the good advice and discard the negative ones.
MatthewHD gave some good advice in his last comment. Slide over to a toy shop and get some dinos and action figures, small and large.
Study the basics. Anatomy, take your time on details and use the toys to experiment with scale and proportions of the build.
It looks like you know what you want to do and how it should look but the lack of training in scale and depth compromises your work. screw the shades and the muscles for now, get the size right and take your time always. When you get the hang of the scale and proportions of the anatomy and build the muscles, veins, shades, depth will follow and fall in place.
And keep making block figures, no need to shade them yet. (the size looks very good on the last block figure you posted)
Keep the pen lose and light. No determined lines are needed. The best work is born from lose shapes and clutter.
Keep going Mr. P. Repetition, repetition, repetition. It is the cradle of progress. Ones you are sure of the dimensions move on to textures. One study at the time.
The hands and feet study looks good, but disappears in the finished work. Maybe your rushing it a bit, maybe... ~shrugs~
No rush. Have fun.
_________________
I'm not here to enjoy life, I'm here to withstand it.
AAA
Crosseyed God
:::)