These are both images I picked to practice pixeling. Done using The Gimp.
The first is from page 21 of the Dover edition of
Constructive Anatomy by George B Bridgman
http://www.archive.org/stream/constructiveanat00briduoft#page/40/mode/2up (it ends up being on page 40 on the online version):

The second is a portion of Hive by James Jean (
http://www.jamesjean.com/blog/C47057/hive)

In both cases I picked someone else's content so I could focus on technique without fretting over the original too much.
I am actively working on the second, though I will take C+C/suggestions on either.
Thanks,
Edwin