couple of storage areas we usually forget about--under the bed you can put those plastic tubs for under bed--if the new bed isn't one that sits very high off the floor, you can also put bed risers in (can find at at Bed,Bath & Beyond--college kids use them all the time in dorms) and gain even more space. Also a shelf ABOVE your windows for those items that don't get used all the time uses that "lost" space well. And a shoe hanger on the back of the closet door can work well to keep rolls of stablizer, fusibles, etc (even fabrics rolled).
My sewing space is also used as a bedroom for overflow guests and has a trundle twin size bed--I don't have a mattress on the trundle part--it holds bat scapes and wideback!