No, we'd need a plural to justify using "are". "What things are there in your bed?" This also assumes that your bed has several things in it. By the way, do you mean "bed" or "bedroom"? It's natural to ask a singular question if we don't know whether the answer will be one or many. "What's in your bed?" (we don't even need "there") "Who was at the party?" (yes, the answer can be a list of people) "What's in the fridge?"

"What is in your bed?" would be most common. If you are pointing to a specific place in the bed : "What is there, in your bed?" It would be interesting to know the context!

Hello :) Are there many things in your bed? Because if you mean one specific thing you ask: "What is there in your bed?"

What do you mean exactly? Why not to ask "What is in your bed?" or "Who are there in your bed"?