We centered our ceiling fan over our bed. Our room is a bit smaller than yours. Ignore the unmade bed. Waiting for the sheets to come out of the dryer.

Do they have to know the position NOW? can't they just wire it and wait?

any of these help?

The peak of vaults above appear to be centered in the room. Our vault is off center. The electrician will put it wherever we want it but we'd like to be confident in it's placement to avoid having to swing the cord/wire over to a hook someplace else.

it's fine to have it over the bed if that's where you want it.

this one is not centered

or, move it over to the center of the room, even though it's off center from the vault. That's fine too.

similar to having the dining table light over the dining table, even though it's off center in the ceiling.

Well I can answer this as I have lived with the same issue. We hung a chandelier in our master bedroom. We built the house and obviously all lighting is completed before moving in.
It made the most sense to hang it in the center of the room.
When I walk into the room and I turn on that light, I notice the light first and the bed later.
Go for the center of the room. It is not like a dining room where the light must be centered over the table.

I would vote for the light to be centered over the room.

Mine is centered with the room.

ETA:

Oops. Now that I look at it, mine is not centered to the bed or the room. It is centered to the door used to enter the room and the fireplace, which is also where the peak of the vault is. Builder basic tract house...

Oops after looking at mine again I just realized mine is centered in the room which just so happens is centered to the bed.