One thing I will mention is that even with the best laid plans - you will find your studio will evolve a little as you use it. 2 years down the road from when I built mine, I -think- I have the ideal studio but I was still eyeing that Ikea catalog and formulating ideas. (That space under the sofa bed is just wasted space... )
I'm also in the basement. It's about half of the basement. The room was originally an "in-law" suite - so I have a full kitchen along part of one wall. This is invaluable. I don't have the headaches and other issues I used to have because I got absorbed in what I was doing and forgot to eat, or left something in the microwave for a day, or had to reheat it 3 times.
The floors were done with "Dri-core" and then laminate over top of it. We get cold in the winter and the basement does stay very cool most of the year - so I have 2 space heaters. One oil filled and one parabolic. There's a rug under my long arm so that my saddle stool doesn't roll away with me (anymore). I also humidify the room in the winter, which alleviates the need for thread treatments and eliminates thread breakage. This came about because where I am - it gets really dry in the winter and the furnace doesn't help that! When we tried to turn the whole house humidifer up, we ended up with windows that dripped water upstairs. I also find I have fewer sore throats and less fatigue problems down there as a result.
As much "storage" space as you can manage. I have pegboard on portions of 4 walls, I have Alex (Ikea) drawers under my Long Arm and under my main sewing machine and a couple of "armoires" that hold batting, fabric and quilt tops waiting to be quilted. My cutting/Do everything table is made from Expedit (Also Ikea) book cases connected together and on a base that we put wheels on then covered in MDF and (4) 24x36" cutting mats are attached to the top. My pressing "station" folds away against my cutting table if I need the room, or has 2 folding legs and a piano hinge to the cutting table to keep it in the usable position.
All of my tables are at standing height. My sewing desk and the cutting table are at 35 1/2". I found this the most flexible for me. Easiest on my back (disk problems) and if I want to sit, I have higher chairs with good foot rests. I regularly spend 10 hours a day down there between sewing, quilting and servicing.
My lights are from Ikea - they were clearing them out for $3 fixture. They each hold 2 halogen GU10 bulbs which we're slowly converting to LED (though I do love the warmth of the bulbs. I take after my cats that way, I guess). There are 12 fixtures in the whole room, with 2 of the fixtures in the "kitchen"/"Seating" area on a separate switch. My LA has florescents over it - (3) 4ft fixtures which are over and above the Ikea lights and also on a separate switch along with one set of the halogens.
The way the room is set up, I have room for my sewing, Long Arm, servicing sewing machines and 22 sewing machines on display and (mostly) convenient for use.
I think there was a thread here once where someone asked what we call our sewing areas. Mine? I call it the Ikea showroom.
Though more accurately, I guess it would be the
Ikea Hacker's showroom.