When booting into Windows PE with the HP Proliant BL460C G8 server (and maybe many others), it will load WinPE and go into a black screen, nothing can be done.
This is because this server does not support WinPE 5.0 (yet) which Configuration Manager 2012 R2 is using.
To fix this problem use the Boot.wim file from a Windows Server 2012 media, and import this into Configuration Manager by using the Console and right clicking “Boot Images” choosing “import”. (Remember to place it on the Distribution Points allso)
Use this image and the servers can now boot again, the downside is that Configuration Manager 2012 R2 does not give full administration possibilities with the WinPE 4.0 image, so it is not possible to import drivers using the console. But none the less it was not nessesary in my case.
I hope it will help you in your struggle.
Update: HP have supplied the following links for this issue, but i have not tested any of them.