Looking good so far. I like what you've done with the shading on the figure. The colors on the girl's face looks good. I'm sure you will be adding texture later on. I'd like to see the latter stages of this painting. I like where you are going with it.
I like the idea of a 100 face challenge! Really digging number 46. You seem to have a good handle on rendering. I can see that with the digital portraits and the bat drawing. Not sure how long each face takes you but one suggestion I would give you is maybe after every 10-20 faces to study some facial construction or anatomy in an area you find the weakest. Say that for the first 20, the biggest issue you find is the nose, then study the nose for a few days, and come back and do the next 10-20 with the knowledge you've gained. I always try to review some sort of weakness even if its just for 15 minutes before going in and drawing a head from reference or imagination. Hope this helps! Keep posting!
Hey man! Loved the chalky version of the drawing, I can see more shapes on that piece. Don't blend too much! You are the colour and shade master! Keep studing the fundation, and you will fly!!! :D