EDIT: THE FOLLOWING BUGS ARE NOW LIVE. THANKS BLIZZ FOR LISTENING TO OUR FEEDBACK AND BUG REPORTS. /sarcasm
Currently in the beta hundreds of helms are bugged. Blizzard used some kind of automatic program to "fix" some clipping issues and they didn't notice that a lot of appearances are not working as intended.
Some of them have wrong textures, others are poorly positioned, others are way bigger or way smaller. Either way all reports are being ignored.
Here is a partial list with some of the bugged helms, taken from reports on reddit and the official forums:
*Conqueror's Crown
http://i.imgur.com/f1VMlYf.jpg
(In some races it looks totally white)
*Deathmantle Helm
http://i.imgur.com/AgUzHlE.jpg
(Doesn't cover the nape)
*Demon Prince's Ascendant Crown
http://i.imgur.com/T6eo19O.png
(It's way smaller on some races)
*Primal Gladiator's Dragonhide Helm
http://i.imgur.com/3vurZhi.jpg
(It's way smaller)
*Darkfang Mask
http://i.imgur.com/oMe334Q.jpg
(Wrong color)
*Vengeful Gladiator's Felweave Cowl
http://imgur.com/a/05gaz
(Wrong position + clipping)
*Primal Gladiator's Helm
(Instead of covering the eyes it covers the forehead)
*Bloodfang Hood
(The red eyeglows are bigger and sometimes disappear.)
*Judgement Helm
(Way narrow, dwarfs' noses clip through it)
*Helm of Might
(It's way smaller on some races, causes a lot of clipping)
*Conqueror's Kirin Tor Hood
(Doesn't show your character's hair)
*Demonkiller Mask
(Red instead of blue)
*Springrain Headpiece
(The eye particles are different)
*Chieftain's Headdress
(It covers the eyes instead of the forehead)
*Deathmist Mask
(Way narrow, characters's noses clip through it)
*ALL ENGINEERING GOGGLES
(some of them are way biggers, others way smaller, others are above the eyes, etc.)
*ALL EYEPATCHES
(they are too far away and don't cover the eyes)
And the list goes on and on and on...
¿Do you think Blizzard is going to fix it before release? If you want to help, please make a thread on the official forums. Lets get it fixed soon.
Thank you.