M.H.
Did you switch him to the toddler bed so the baby could have the crib, or was he climbing out of it?
My son slept in the toddler bed for three months and then decided to sleep on the floor. He has been sleeping on the floor for just over a year now (he is 3 1/2). I don't allow him to sleep behind the door, in case there ever was an emergency, like a fire.
At first, I tried to keep him in the bed, but decided as long as he stayed in his room and was sleeping normal that it was fine. He still very rarely sleeps in the bed.
We als tried a full bed vs. toddler an there was no diff.
If you stick to the toddler bed, try putting it in the corner so it is somewhat "enclosed". I like the others' idea of a canopy.
I have heard they will choose the bed after a while for the comfort, just not in my case.
Good luck.