Make it as pretty as you can! You have to like the look, not just the function.
Choose a paint color that's light and neutral but cheery, so that you can accessorize in pops of color. (I chose pale yellow, and I accessorize in turquoise and black & white.) Your sewing room will get so "busy" with color and stuff, that you'll appreciate some uniformity of color in the furniture. I painted mine white, and have lots of IKEA furniture.
Lighting is crucial! Do you have enough outlets and surge protectors?
Put your sewing machine in front a window with a view, if at all possible.
Best thing you can do for comfort is make sure your machine table, cutting table, and ironing table (board) are all at the most comfortable height for you.
Most of all, take your time. Live with the first arrangement a couple weeks or so and ask yourself if it's working or what would make it better. Don't settle. Just resolve that it will be your happy place eventually, but nothing has to be set in stone immediately. If you rush, you'll regret it. I was happy to let my room evolve and suit my style.
I also like to label everything with similar looking labels. You can find my sewing room in a different thread.