We did ours. I used a very low setting bed and a long low 6 drawer dresser on the end under the window . We have a closet along one wall that goes the entire length of the wall and only hangs shirts because its only about 4 feet from the floor.

Now I'm sure this will sound weird, but here goes. In my old house I had knee walls. I didn't like the look of a bare low 6 drawer dresser without the mirrored top that went with it (it was a hutch mirror top). I cut down the wood and framed it around the mirror (let the excess fall behind the dresser-no glass cutting) and made a shorter version that fit perfectly into the knee wall area. (years ago, no pics, sorry).
You could also use one of those inexpensive long mirrors meant to hang on a door. Turn it sideways and frame it out to match the dresser. While it's too short to actually use as a mirror on the dresser, it gives the illusion that it's a full size mirror. Or if the dresser has a matching mirror, either attach it to the wall or add a cleat to the back of the dresser to hold the excess height.
Illusion is everything!

Have you checked Houzz? So many great attic bedroom i inspiration photos. We did ours a few months ago, and it was a big help. Just use keywords "attic" in the bedroom photos category.

For kneewalls, really, buit-ins are the way to go. Furniture can be very, very difficult, depending on the height of those walls.. A good carpenter/cabinetmaker can turn the whole thing into a functional space, even with all of the angled ceilings and short walls.

This post was edited by shanghaimom on Wed, Sep 25, 13 at 18:31