My walk-in freezer is developing stilagtights (ice castles) on the floor and cieling in front of the evaporator coil.MY drain pan is not plugged when I pour water down it.

Check the length of the defrost cycle. While in defrost, the ice and frost formed on the coil will melt and sometime turn into vapor. This vapor hits the cold surface and condenses into water droplets. When freeze goes back into freeze cycle, they freeze. Seen this many times as defrost is 45 minutes or longer and many times it is not necessary to have it that length. Next, turn off lite, go into freeze and close door. If you see lite anywhere around door, air can get in and cause a similar issue. Door should close and seal.

Check for vapor leaks at the seems and in the area where the stalactites are forming on the ceiling and below where the stalagmites are forming on the floor. It is likely that you could also have a vapor leak on the door seal causing a large inrush of moisture or a small one on the seems of the freezer. Note I am a Food Safety Auditor this is a common problem we see several times a month and it can be fixed.

You should check for air leaks around the door gasket or any other openings in the compartment such as where pipes or wiring is going through the wall. It sounds like a moisture problem from moisture being drawn into the compartment pass door gaskets or access holes.