How to get rid of the "Other..."-Account on the login screen?
Have you tried the sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow SHOWOTHERUSERS_MANAGED -bool false in the terminal? This turns off showing some of the other user types.

Doing some additional research, it looks like this has been somewhat addressed in this post on https://superuser.com/questions/70156/hide-users-from-mac-os-x-snow-leopard-logon-screen