From a design aesthetic point of view I prefer ceiling fans over split system units as pictured. Ducted air cons are great as you can conceal the vents better - but ceiling fans are great in bedrooms for people that don't like sleeping with air con units on :)

what about white for the low ceilings and black for the high ceilings where the contrast will stand out against the gorgeous timber beams OR what about white for the low ceilings and timber for the high ceilings to blend and not detract from the beams OR why not please my husband and try his choice of silver!

If you mean 2700mm ceilings which are quite normal height these days. Ceiling fans a widely used throughout homes with that height ceiling. The fans will not make the room appear smaller, it depends on whether you want the fan to be a feature or blend in with ceiling. I have brushed chrome fans with lights in every bedroom. My ceilings are white and walls a light grey. If you want timber, then have timber, if you feel that will blend in with furnishings.

We have the same - low ceilings but I console myself that the house is easier to keep warm in winter! Photo 1 is our bedroom fan, which I don't like - it feels intrusive in the room. Photo 2 is our fancy "low ceiling" fan, which we love. It doesn't announce its presence like the other one and is super quiet and efficient. Photo 3 is the remote for the loungeroom fan if you are interested in details. I highly recommend it - it was expensive at $400+ but worth it