I had to do a Cinderella cake for a birthday.  The mom picked out a 1/2 sheet cake with Cinderella star piped with buttercream.  So the cake was a picture of her from the mid chest up.  Everything looked great, but her face.  I redid it 3 times and it never was "right".  The mom still loved it, but I am not happy with it.  I want to improve.  I've been searching for any tips or videos on how to do faces in buttercream but have not really found what I'm looking for.  I'm hoping someone here might be able to give me some pointers.  Thanks in advance!!

I can only tell you how i do it. I make a copy of whatever image i want to use and blow it up to the size of the cake. then i lay the image on the cake and "stencil" it by following the outlines of each shape, nose, eyes, etc... with a needle or skewer . then pull the image away and have the tracing left behind. 

i find that whenever an image seems awkward it's because i haven't matched the eyeballs up properly, so i take extra care with the eyes. 

Frozen buttercream transfer.  There's a tutorial on here for it. http://cakecentral.com/a/how-to-create-a-frozen-buttercream-transfer. hth