a little tip I have is to make the mouth bigger than the teeth so it looks like the lips are stretched back, also add a layer of shadow to cover some of the features so the viewers mind has think up of what it would look like in light. just a little tip.
A lot of my choices for this were intentional and this character doesn't have lips
I just wanted to make something scary for the fun of it but I'll keep what you said in mind for the next time I draw something like this