OneBroad: I have 2 of the IKEA tall Billy bookcases in my sewing room, but i don't use them for fabric (originally thought I could). I use & love them for books and some equipment/supplies, like paints, stamps, etc. For fabrics, be careful that you are aware how narrow the shelves are: about 11". Many plastic boxes are wider than this. Although U can get extra shelves for the Billy's, fabric visibilty IMHO with them isn't great.
I suggest thinking about how you can get usable-sized fabric samples of all your fabrics within easy "eye-sight," so U can see them all at once. I decided this was a huge priority for me as using them together matters a lot for my work. I also decided that samples of everything all 2gether needed to be in my room but the fabrics themselves could be stored elsewhere, as long as they were easily findable and accessible (described in my previous post below). I use kid sized hangers to individually hold samples of each of my 50o+ fabrics, and this is the single most important thing in my sewing room. If I had no closet I'd make hanging rods out of dowels and chains suspended from the ceiling to hold the hangers. In the (leftover guestroom) closet in my sewing room I took out all the original fittings and put in ClosetMaid from Home Depot, so that I can have multiple hanger rods spaced close together vertically to hold the samples, plus a few wire shelves to hold boxes with pattern pieces and fabric parts in progress.

VMiles, how wonderful! It took me a long time too, to realize that I/we live here. My sewing room/studio was a "guest room" alternate, with trundle beds and a cutting table i could dismantle (with a lot of time)for the once every 2 years guests. The new, never-used trundle bed went to Salvation Army on my husband's prompting and I now spend every day in my completely dedicated sewing room, next to my DH's completely dedicated writing room, that also used to be a bedroom.
What I'm learning from these wonderful posts are 2 things. First, it pays to invest in organization for sewing. Investing in organization is always hard, as it's expensive and time consuming up front. Sewing focuses the issue because it takes so many little and big things to do it. Think of how many notions one has! But the payoff is incredible although later. In my room, I actually for the first time know where everything is and i'm comfortable and love being in there. Organization means that you can focus on creativity and productivity and not on hunting. Hunting is stressful and detracts from life.
Second is that having an avocation like sewing forces us to focus on what is truly important in our lives. We have to make choices: a once in a while guest room, or a room to live in and truly enjoy every day.

It looks like you're off to a great start--I also use the same IKEA table legs and keep them at the top height so I can stand when working or use a hydraulic adjustable coved bar stool, $50 at Target and worth every penny. You can get it to exactly the right height & its comfortable.
To supplement daylight I suggest 48" double silvery florescent fixtures from Home Depot. They're sharp, professional and modern looking and will hang from chains (included), from hooks screwed into the ceiling or beams. They come with plugs and pull-chains, or you can wire them in if you're so inclined. Mine are wired into track light strips that were previously installed on the ceiling. I've put into them HD true-daylight Blue-ray tubes ordered on the web. I have *5* of these in my dedicated bedroom-sewing room and it is wonderful to have enuf light to be able to work anytime *and* be able to match fabrics perfectly.
I have a lot of fabric and store it in another storeroom in clear plastic boxes (all the same), by number. A sample of each fabric cut to the same size (6" wide by 18" long) hangs doubled over an individual kid size hanger (good plastic ones at Target) in the closet in the sewing room. I use a tagger for fine fabrics (from ULine on the web), to put on a tag with the fabric number, and also to tag across the fold of the hanger to keep the fabric from falling off. The saample is big enuf to match fabrics and play with, and the number tells me where the fabric is in the storage space. You can organize and reorganize the hangers any way you want--by color, by prospective projects, etc. It's flexible! New fabrics just get the next number available, irrespective of color so you don't have to stuff the next, say, pink one in an already overflowing "pink" box.