there is a seperate utility for boot screen (used to have it, now i forgot what it's called), logon screen is also changed by another free utility (i think object desktop do that also), i'm not sure about icon set, as i never had much success with that anyways..
it's all safe except the possible lag in your system as it costs hefty resource :|
lisp hacker :D
running: FreeBSD 5.4 - still learning :D
develop with: SBCL + emacs for lisp, Anjuta IDE +gcc for c, SPE for python..
browse with: opera