I've turned an eight-bottle wine fridge on its side. A BacoEng 2 litre growler fits with tap and mini CO2 regulator attached. There's even room for two kegs with taps and regulators! I'll test it tonight to see how long it takes to chill two litres of water from ambient to 10 deg C.
Looks like it could be really good...cool ahem.
Being peltier it should be ideal for any way up. Many of the chinese units have fans on both sides too so you should be good for an even cooling. Only slight issue is the temperature differential so it may only get 8 degrees away from ambient. You can get more - just takes more power or double the cooling units.
May also have to re-hinge the door..... or fit gas struts and fog machine
I filled the keg with warm water. The fridge dropped the temperature from 27C to 13C in four-and-a-half hours. The 'stat was set on 10. This morning the keg was at 10.5C. So it looks practical. I'll check the daily energy consumption over a few days. There is an internal fan so the temperatures will be pretty even.