Originals with orange pumpkin are considerably better because:
1) It's four times as readable (instant understanding that this is a pumpkin we're looking at)
2) Blue + Orange = Compliments which is definitely more pleasing to the eye

This seems like a very tricky project to render properly and I wish you the best of luck.  Great effort so far but don't go in that latest post's direction at all.

He's talking about the light blue highlight you put across the little guy's forehead.  When you wear a brimmed hat it casts a shadow on your face.  So having a highlight right where the hat would cast it's shadow is incorrect.

Eyes should be centered vertically on the face (add a little more forehead to the top of both).  Good benchmark for ear sizes (especially on a basic frontal pic like these) is from the top of the eyelid to the bottom of the nose.  So extend the ears down a little bit.  Female faces generally have less defined bone structures.  Removing that furrow line right below the ear on the cheek will likely make the face more feminine.  In general, the features of the face seem flatly placed on instead of actually being built in (especially evident in the way you treated the bar code on the man's head (it doesn't even bend to the round shape of a forehead).  Try treating the eyes as actual spheres and allow how the skin around the sockets is formed around that to come into your work.  Irises generally don't look like that with the rays coming out of the pupil.  Also highlights are rarely contained with the pupil itself but usually overlap it and are on the iris.

As a compositional sort of critique it could be neat if the two people were looking more towards the center of the piece and outward at the viewer instead of straight ahead.  All of the hairs, from eyelashes to eyebrows are pretty excellently rendered.  I also think the idea of the scene is pretty sweet.

Overall these seem like really terrible references when you could very easily find pictures of people looking straight on into a camera.  You will learn a lot about facial anatomy from this piece, but, there are a lot of basic errors that show a general lack of experience that could be remedied a lot quicker from a ton of studies with a less intensive medium such as drawing.

HMC: the bone structure in the female head should be less evident then in the male.  currently the cheeks are pulled in very ridgedly while they should be round (particularly the line formed by the edge of her face on our right is very bony and awkward).  also her neck is given more definition then her male counterpart (the highlight at the bottom center of the neck could even be misread as an adam's apple).   eyelashes typically are more pronounced on the outer edges of the eye away from the nose and here they are almost entirely absent.  i understand you're trying to give a sense of the angle they're facing with this but i still feel adding more could give your character a more feminine touch.  the folds of her cheeks seem way too apparent and awkwardly shaped for a near expressionless face.  overall i love the stylization, exaggeration, and lighting on these, they look great. 

The four dark pixels at the top of the skeletons head were reading as ears to me pretty badly.  I thought it was a panda until i read xion's post.  These are great little sprites though and lovely for 3 frame animations.