I think both of Matt's first two plans are your best options.
For starters, the hinged bridge will give you access to the room through your door. (Just be sure that you have accounted for where your door is located and how far it swings/travels.)
Secondly, from my own failed experiences, plain, "boring" loops are best avoided if at all possible. They're easy and cheap...but they get boring quick. Matt's plan alleviates that problem.
The curse of modeling in O will always be trying to make your curves as wide as possible. Given the size of your room, you'll be hard pressed to come up with something better than what Matt has provided you with.
For what it's worth, I'm working on a L shaped layout where the long part of the L is 25 feet long and the short part of the L is 15 feet long. I'm going with a double track main line. The best that I could do on the shorter 15 foot section are combinations of 80/72 curves on the outer line and 72/64 curves on the inner line.....and I've got 4 more feet to work with than you and no door to contend with.
IMHO, Matt's plan is really neat and you'd be hard pressed to better it.
Than again, that's just my opinion.