There's no way to change the design of the lockscreen controls using the API, as far as I know - it just uses the system theme, so on stock ICS it'll look like stock ICS, and on a HTC phone with Sense it looks like Sense. Anything beyond that sounds pretty difficult, and a bit of a hack (see anything that used lockscreen controls pre-ICS, like WinAmp).
I have found the source code now (wasn't on the main Sourceforge page, but is within the SVN pages), so I'll look into this when I get the chance.
Edit: Looks like someone else has already made some changes to use the ICS style, and added the menu button here -
viewtopic.php?f=5&t=8497&start=105 but it's also gone quiet. Might try and add the lockscreen controls to this source instead, though I don't want to fragment things too much.