[leviz1]

I'm trying to build a virtual environment that will look relatively natural for an experiment and could use some help:

I have loaded a model of a room from 3d warehouse but need to add a ceiling for it to look normal
Is there a way to add a simple neutral color/ pattern ceiling at a specific height? the room I need it for is pretty big so the ceiling should be long/ with length by demand
couldn't find anything suitable on 3d warehouse.

Thank you in advanced