I'm of the mindset of "less is more".
Here is my last layout of 11 X 13. My next will be with less track.
A shelf layout can be very interesting and fun to run with minimal sidings and destinations.
Have you considered modelling a branch line?
I'd go for more than a radius of 22; you have the room for it and could get away with 32 inch radius and trains look nice on a radius like that.
You do not need a lot of lumber to make a shelf layout. You can put a 12 inch shelf on very strong brackets and it won't be intrusive on the room especially if you have it at chin height. This way you can still use the room as a guest room or office. Check out the pics of my past layout.
Here are links to my old narrow shelf layout to give you an idea what can be put into a shelf as narrow as 9 to 12 inches:
http://www.modelrailroadforums.com/forum/showthread.php?t=16941&highlight=scenes+narrow
http://www.modelrailroadforums.com/...ighlight=scenes+narrow+shelf+layout+continued