Yes you can, but it's not easy. I briefly spoke to to one of the unity devs about this the other day.
You would need to edit one the m10 files in the lockscreen apk.
If you don't have any prior knowledge of editing m10 files I suggest talking to either flemmard or diamondback at the virtuousrom irc channel.
Sent from a phone that is not a HTC Desire Z
Last edited by cjward23; 20th July 2011 at 04:39 PM.