Silvers.cfg (by SilverShot): This config was made for ALL games except L4D/2, for those you would need to edit the config to set the correct particle color numbers. I might make a command to convert configs from ALL games to L4D/2.
Checkpoint_Arrows.cfg (by moekai): Made for L4D/2, can be used in all other games.
I created decals or sprays to trace their shapes in-game and avoid creating symmetrical shapes by hand.