Do not lean a cello up against a wall or corner. It is much safer lying on its side on the floor near a wall, but be careful not to place the instrument near baseboard heaters or heat vents.
Never leave the endpin out when the cello is lying on the floor. Others might trip over it. Do not leave a cello case standing up in a room. Passing people, shifting rugs, gusts of wind, etc. can knock the case over and damage the cello.