Xlockmore is an enhanced version of xlock. Xlockmore incorporates several new commandline options, which allow you to run it in a window, in the root window, in a different size/location, change the size of the iconified window, to install a new colormap and delay locking for use with xautolock.
xlock(more) is more than just the modes, there are a few password mechanisms and public lab switches that can be chosen to be compiled in. I eagerly accept patches and improvements and ports for xlock, I would rather get a new interesting modes.
Many people have helped me maintain this over the years, most notably Jouk (Jacob) Jansen and Tom Schmidt. There are 100+ modes so I am sorry if I neglected to mention a personal favorite.