If it's the other way and the body seems to be getting bigger, the person may be "concerned" that their body will burst through the walls and crush everything, including the other people. It may be that you are the giant and everyone else is 3 inches tall. It may seem like your body has expanded into the size of a galaxy. It could be that your body gets small and then gets big and then back to small again, etc. Any of these kind of things are possible but, again, it doesn't mean that any of them will happen on your trip. The point is to be as aware as possible of what can happen, not to worry about anything because you know that the LSD is responsible and to just enjoy the show, whatever happens.

If you are lying down on the floor, looking up, a chair will seem to go very high up, the way a little child sees it as it crawls underneath and through the legs. An adult who is tripping might crawl underneath the chair and through the legs and relive all of that. If the adult's body is too big to fit through easily, then substituting a table for the chair will have the same effect.
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If you are on an elevated platform looking down at the other people, it can seem like you're standing on the floor with the others even though you are still up there on the platform. This is somewhat similar to the example of someone lying down on a bed and it seems to them like they're standing by the bed, looking down at their body which is lying down on the bed the whole time.

Don't waste time and energy trying to make logical sense out of these things. LSD is way beyond limited logic. Logic says that something is a pencil or it's not a pencil. The truth is that something can be a pencil and at the same time, not be a pencil. Reality is not either-or divisive logic. It's more like both-and unity. When tripping, it makes perfect sense to look at a pencil and say that it's a pencil, but it's a lot more than a pencil. As explained earlier, a pencil is a whole lot more than just a pencil.

There are other possible depth perception changes. If you're in a room, the distance between you and objects can change. As explained earlier, an object will move, but most likely stay in the same spot, the way someone doing Chubby Checker's dance, the twist, will twist back and forth, but the feet are in the same spot. If the object doesn't stay in the same spot, it can seem like it's coming towards you, not in a threatening way, or it can seem as if the object is moving further away. Even if an object is against a wall that is facing you, it can still seem like the object is moving further away. Simultaneously, some objects may be coming towards you and others moving away. It's like anything goes.

The whole room itself can seem to be expanding or contracting or be breathing in and out, just like a single object can seem to be doing that. The objects and the entire room can be doing all of this according to how you think and feel. If your mood or thoughts change, the "action" in the room and of the room can change and if music comes on, then the objects may start singing and dancing, with the room vibrating or flowing to the music.