Maybe this is too obvious, I would start with a scale drawing of the space and make templates of minimum sizes you need for sewing, cutting, quilting areas etc. If you machine quilt, Kola makes some great tables, see how they would fit. Don't forget to make walls with actual usable height so you know where on the floor you can actually stand up. I love having the window to my left, I can turn easily to see the view and the light is good. After you figure out furniture, storage, draft a lighting plan that puts it where you need it for sewing, cutting and your design wall. There are some great fixtures that use natural light florescent bulbs. You will have a great room.