Okay, here's what I've got - its not going to be an easy one. I'd recommend downloading the photo and zooming in to about 300% or so.
I think I understand the space you're in - its similar to a friend of mine's house.
Okay, here's the pertinent design features.
1. Curtain divider. With the lack of space, it'd even be tough to do bookshelves there. I'd get some of those nice tab curtains from Ikea and hang the rod from the ceiling.
2. Track lighting. The best part of having a slanted ceiling/walls is that you can aim track lights very nicely - and they're cheap - you coiuld do the whole room with two sets for under a couple hundred.
3. Adding in wardrobes (for clothes), a desk (to put your crafting stuff in), and a bookcase (for books, craft materials, etc.)
4. Adjusting your cubes to fit between the poles. That way you can take advantage of the space between the poles as best you can.
Hopefully this gives you a little space of your own plus space to walk in. My architects were sitting and playing with the design over lunch, and they got really frustrated, so don't feel bad you can't figure it out! Your biggest deal is going to be dimensions of EVERYTHING. You are not going to be able to fit a lot of stuff in that room unless you measure everything, the room, the lighting, the furniture, etc. and then draw it to scale.
Good luck!!!! I think I like the best that most of this can be bought inexpensively at Ikea and other furniture stores. I'm guessing no more than $700-800, less if you can find thrift store pieces or make your own parts or hit a good sale at Home Depot on the lights (or can buy at a builders resale shop - PM me if you're in Illinois and I'll give you a good one). Plus, all of it is reusable by your parents or yourself when you move out!