Sometimes you never know who made your poster (maybe someone who liked your resume?) Right after I rushed, a member came up to me and said, "I remember your poster! It had those gorgeous stars all over it!"
On the bathroom mirrors, and doors, hallways, doors on the stairways and in the stairways...but NONE downstairs, of course.
Some chapters have a committee that does them for particularly desirable PNMs. Or for towns where you need members. Or majors, or talents...etc.
I'll never forget the moment, early in pledging, I first saw a decorated rush poster under my Big's bed that read, Suicide ZZ. Suicide?! Whatever could THAT mean? She explained it was meant to pump-up the house for rush, but I didn't buy it until I was initiated and on the other side of rush.