After a restore the iPhone is in DFU mode. What now?

To restore an iPhone with custom firmware (cfw), you have to put it into DFU mode before starting the restore. If you say that after the restore the phone is still in DFU mode, then something got terribly wrong. Just start over. Make sure not to use simple mode when creating the cfw in sn0wbreeze.

But probably you didn't mean DFU mode (black screen), you meant the USB logo. This is Recovery mode. Or if you can dial emergency numbers, then the phone is just not activated. This is a different question.