1. A design wall is a great idea and it takes up no floor space.
2. I bought some stacking rectangular baskets at Lowes (closet organizer dept) that I use for keeping the components of WIP projects organized. I think that's been very useful.
3. You mentioned that you have two windows. You might consider locating your machine work station in front of one of them, particularly if you have a good view. The extra light will certainly be helpful.
4. Since your room is fairly small, I agree you should consider double duty equipment (e.g. cutting and pressing).
5. If it's in the budget, use a small flat screen TV that you can put on a shelf up out of the way.