FileVault Encryption

Not sure I understand your question. When you use FileVault, you must sign on with your user name and password as that's the way it works. You can not bypass the log on screen with FileVault turned on. Otherwise, you have to decrypt and remove FileVault.

 

They grey screen is necessary for unlocking the disk. The device cannot get to the Macintosh HD partition otherwise, to the system. On correctly configured computers it skips the regular login screen. Encrypting the disk takes a long time and you have to wait until it is completed to reverse the process (which takes just as long).

It should not show any other icon on the unlock screen, however. Just your user accounts. Perhaps it is because the encryption is not yet complete.

 

My machine has been doing the encryption all week and it's still isn't finished. Hopefully you won't have any issues.

 

You can't have automatic login with filevault enabled

 

I did a usb2 full disk encryption on a 2 tb drive with 200gb free space. It took 29 hours total.
Just to give you an indication. My usb2 on my old imac gives me about 35mb write speed. Quite terrible.

 

I've had this happen a while back running something between 10.6 and 10.9, or I may have been using PGP's encryption product, can't recall, but it did seem to hang (not just take a long time) and needed a risky hard shutdown, after the reboot it then actually started to encrypt the disk and it was smooth after that.