I have the top room above the garage - 34' x 28' I think. The staircase is 4'9" wide so I can get furniture up there to practice upholstery. There is a shower room and a recessed kitchen with a deep craft sink along the south wall leaving the rest of the space for a studio. If we have lots of guests staying over I can retreat there and be perfectly self-contained.
At one end of the room I have a stove with two couches, a television and CD player and window seats that hide bedding and craft items I don't need to get at very often. Under the built in corner TV table I've stashed my photography stuff - frames and card making things - and I've velcroed a curtain there to hide the mess. There are floor-to-ceiling shelves for books and magazines in that corner too.
Along the north wall there are five windows overlooking the garden and on the opposite wall is a design frame. In the recess created by the staircase I have shelving for fabric and very narrow shelving for jars of notions.
I use the kitchen shelving for overflow jars of buttons and ribbons and bag making notions.
I'm very lucky that the garage was built away from the house though it's not advisable to traipse across the yard in the dead of night when the weather is vile, there's 4' of snow or wild animals about but, if we had attached the garage to the house as originally intended, my studio would have been the master bedroom and I'd probably have had to use a much smaller room for my sewing. I've created a central sewing area that could accommodate other people too but is currently full of patterns and works in progress; I'm not very tidy. The only thing missing is someone to share it with - I find I do a lot more work when there's someone else to chat to but I live in an area where a lot of quilters have their own spaces that range from closet size to a spare cabin in the woods and we just get together twice a month to show and tell or learn a new technique. As I said, I feel very lucky to have this dedicated space.