Not too bad actually for a weekends work. I think the nose/mouth guard part (don't know what you call it) is a bit to long and the bits that stick out of the sides of the crown need widening. Changing these will make the piece a bit less angular and give it a more natural curvature. I would also make the curve more pronounced between the front and back of the Bio, it looks a wee bit flat. Of course all of this depends on the shape of your mask if you intend covering one.
Looks like you've got the symmetry pretty good but it could be improved with further tweaking. It's easy for us to crticise looking at static photos, but not so easy when looking at the live sculpt.
Hope my practical critique is of use and doesn't discourage you, as this is the time to get things right. No point in telling someone after the cast is made.
See you have the alien brewing in the background. Looks as though you are going to be busy.