12' 2" x 11' 4", speakers on the 11' wall. There is a guest bed lengthwise in between the speakers, so they are fairly crammed into the corners. They are a couple feet from the back wall, and flush with the front side of the bed. Imaging is still pretty good, although far from perfect. My chair is backed up to the opposite wall, with a throw blanket on the wall behind me to mitigate reflections. Again, far from perfect, but quite good.
I´m located at the corner of a living room of about 11 m wide, 4 m depth and 3 m height. In practice, the "listening room" is a imaginary area (without a right side wall) of about 3 m wide and 4 m depth. The open wall helps a lot to reduce reflection but needs more power from the amplifier, at least for listening to orchestral music.
12.5 x 12.5 with the speakers placed in one corner where there is also a deep recess in behind. Placing them on any one wall sounded like crap and would have required massive amounts of acoustic correction. The corner placement solved things nicely to my ears.
Main (living) room is ~ 16 x 15 (albeit with an open area which makes the entire space closer to 16 x 20). Ceilings are just shy of 9'. Speakers are along the short wall now, but I'm hoping next year to do a minor remodel which should allow the speakers to be along the longer wall (with the open area behind the listener, rather than to the right of the listener).
Basement is 16 x 14 with 8'ceilings, but the listening area is around 8' from the speakers (and the ceiling drops to ~ 7' at that point as well).