Long arm probably not in that room!!LOL Mine is 14x12 and my "mid arm" is only set up to do twin and smaller. No room to turn around.
Think vertical for storage, add a sewing desk and some sort of long cutting table. Embrace the windows with shades that can be pulled when the light is not needed. Take up the carpeting if you have it and put down some sort of vinyl or hardwood.
Many others will have more ideas, have fun!!!