Room size and floor standing speakers

Should be no problem as long as the speakers do not need to be placed too far from the backwall.
I have Sonus Faber Stradavari's in my office (12.5' W X 21" L X 8.5' H) & they sound fantastic!
You do not want the floorstanding speakers closer than 10' to your listening position or they will be in your face.
12' to 14' should work out very well.
Make sure the speakers you audition are not too deep (18" maximum) & need less than 4' from the backwall.
In the very same room I have had Wilson Watt Puppy 6's & SF Amati's & the all sounded great.

Your room is probably close to average. Yes, it's true that speakers that are too big for a room can cause problems. You should be just fine with many floorstanders.

Your room is not that small. Most speakers will work there.

full range floorstanders for sure

My room is 18x15 and 9 high and I've got my Spendor S8Es on the long wall, about 28 inches out and eight feet apart. Imaging is very good, although stage depth seems a little limited. There are lots of floorstanders that'll work in your room, just don't get something really gigantic with overpowering bass. I think it's all about the balance.