Hi,
Thomas: Thank you 
Glenn: Thanks for the suggestion! Sounds like a good idea, will definitely think about the colored backgrounds when I edit some of these pieces in photoshop in the future.
Verdell: Thank you, glad you liked it 
Made some changes to the last piece based on Johan’s comments, (sorry cannot respond in time to all the critiques) - increased the contrast on the faces based on my meagre knowledge of the skull and facial muscles.
There are some unnatural highlights at the corners of the paper due to scanning, as usual:

At the same time, just to let viewers of this thread see how much contrast really catches the eye. This is something I feel beginning artists sometimes lose focus at. I think it takes courage (as well as knowledge) to really bump up the contrast accurately and in a pleasing manner. Something I always try to work on everytime I draw.
Just compare above and below (heightened the contrast w photoshop, at the risk of losing details in the dark areas,of course) :
