it looks great but i have some comments
the head looks an little bit to big!!! make it an little bit smaller
the alien is looking happy, make him mad

i cant see the teeth very good, but i dont see any sharp teeths in his mounth!! his mouth is also to small.
if you wach the alien movies carefully, you see that his neck is not one object, but has more tubes running out his head to his body!!
the back of his cap on his head is good, but in the middle it is to smooth!!
dont forget the slime when its done ;-)
the body is good!! i dont have any comments on that

sorry for al the comments!!! but i hope you will forgive me!!!
tweak some parts, and this is gonna to be an perfect alien!!