For the calvin and hobbes lockscreen, the posted images weren't at the right resolution/transparency, so for the background, use:
http://blog.mattgnann.com/blogfiles/lockslider.png
and place it as /usr/share/themes/themename/backgrounds/lockslider.png
And for the calvin, use:
http://blog.mattgnann.com/blogfiles/...iderThumb3.png
and place it as
/usr/share/themes/themename/images/LockSliderThumb.png
then restart, and voila! The calvin could use better transparency, there's still a little white around the edges, I didn't feel like fixing it. :P