I have no idea who is responsible for originally coding these, but since a few people have inquired about certain things these tiles can do, I thought I would share them.
There are 4 Floor Tiles : Insta-Kill, Return Home, Mob Restriction, and Unhide.
Insta-Kill - Does just what it says. When a player steps on this tile, they die, period.
Return Home - This tile send any mob back to it's "home"/spawn area when it steps on the tile.
Mob Restriction - This tile prevents mobs from crossing the tile. It does NOT provide LOS checks (mobs can still attack across the floor tile).
Unhide - If a player is in stealth and steps on this tile, it will reveal them.
NOTE: Not tested with the latest ServUO repo.