When wiring the room, make sure as well as lots of outlets, they are on different circuits. Put some of the outlets at counter height. No point in having to crawl under counters to push in a plug. I have power bars mounted on the wall behind my machines.
No windows, that is tough. I would put in a variety of types of lighting and bulbs. I know people have their favourite bulbs, but you need what will work best for you. Overall room lighting, task lighting, lighting over your iron, cutting table and design wall. I prefer to have lots of light around my sewing machines, above, in front and from the left.
I currently have concrete floors. They are hard and cold. My dream sewing room would have heated wooden floors.
When designing a space I like to draw the dimensions on graph paper. Mark all windows, doors, closets etc. Then I make little to scale cut outs of each piece of furniture, or feature I want. This helps me to plan the layout and see where plugs and lighting will be needed. I take a photo of each layout, until I decide which one to use. I do keep the plan and pieces in an envelope until need next time.