Submission for the Weekly Challenge: Greenery.... which I discovered a day prior to the deadline. A little late for the party but under-the-gun. I had to leave a few turtles and villians on the cutting room floor. I will update with more after the challenge.
These portraits are an amalgamation of ideas from the original comics, the first TMNT film and the original cartoon. All very influential to me at a young age (I imagine that goes for many kids of the 1980's)
Characters (From Left to Right):
Raphael, April O'Neil, Casey Jones, Master Splinter, Foot Soldier
Edit No.1: Updated with a proper preview avatar! Konami TMNT Arcade reference.
Edit No. 2: Submitted on time for the weekly challenge but never left the public queue. So this submission was left out of the voting process. So, since rules no longer apply, I've added transparency to make the portraits more defined and clear. | 
Thanks, Sinsky. I'm an independent comic artist and do a lot to familiarize myself with chiaroscuro techniques. Since this comp was only two colours, I thought I'd better take the opportunity to focus on lighting. April was actually the most labour intensive, despite her having the least amount of detail. She started off as Metal Tribute Avatar (Meryl) and morphed into April and kicked off the inspration to do some other TMNT characters. Hope to finish s'more when I have a chance.