I have a vacation property and central air-conditioning is not possible. How do I make ductless units look attractive? Do I disguise them?
Ductless air-conditioning is essentially a window or a wall unit that can be controlled remotely or wired to a switch. Since hot air rises and cold air drops, you should position the unit high up on the wall – it's the most unattractive look but the air conditioner will perform at its maximum ability.
For something more attractive, give up a little performance and place the unit below the window and install a decorative grill for it to hide behind. The grill can be as wide as the window and look like a base cabinet, which will give the room an elegance and depth.
The least attractive cooling system is a window unit, which are common in big cities and stick out from the exterior of buildings, ruining many facades. If you must have one, I suggest covering it with unlined linen drapery to let the cool air through.
Any way you disguise the unit will help with aesthetics but not with air flow: Staying cool and having a good-looking interior is tough and usually something has to give.