Sketch :
from a ripped box :
Looks awesome, I love the eyes 
Only crit I can think of, is that the modeled face isnt as pointy - face isnt as long - as your concept sketch. I hope you dont run into difficulty when modeling the teeth. I reckon the teeth are going to be the most important part of the final piece 
Looking great! The teeth are way too wide though.
Not feeling the teeth at all, too exaggerated. The eyes could use some sort of pupil, and the nostrols could be pitted a bit more and darker to make it look like a real cavity. Good start. Like the concept art, can’t wait to see it finished, hopefully before the 31st.
hum, return to the original sketch :
Modifier subsurt and mirror
cool!
Stay Blending this thing!!! 
i’m not a halloween fan but i like the detail
is the skin displacement map
Looks way better now that you followed your original image, meshs look really clean.
Thanks for your supports, folks .
Now the hair-raising continuation :
Its really looking good now! Keep it up! The teeth seem to fit the character better now.