My sewing room is in a 16 x 16 bedroom in our finished basement. I too use one of the oil filled radiator looking heaters and as long as I keep the door shut it stays toasty in there. It takes a little while to warm up, but it is the safest portable heater I was able to find. I have a mid-arm machine on a queen size frame, my piecing machine and its cabinet and a cutting table that DH built for me. Also in the room is a queen size bed, nightstand and dresser. The chest is now in the closet, lol. Hey, that dresser and chest hold ALOT of fabric. DH put up a new 48 inch 4 bulb fluorescent fixture for me and now I can see all my mistakes. My quilting buddy SIL came up for a 6 days last week and we disassembled the bed and leaned it against the wall so she had room for a portable table and her machine.
I use the bed for laying out blocks because I don't have one of those wall board things, but this past week I developed a new plan. An 8 foot pool table is the perfect place to lay out a quilt! It sits right outside the door to my sewing room. DH offered to take the bed down and store it overhead in our utility room but I haven't made up my mind yet. I am now thinking I will get him to take down the bed and make me a table top that can be placed on top of the pool table so that it is wider and longer.
As for garages, I would be upset if the hubby made me move my motorcycle or my car out so he could have more room for wood working. But I do let him store his golf clubs in my sewing room during the winter months. :)