Start by painting the walls of your sewing room. In general, you should choose a light color to make the room feel brighter and cheerful. Especially if your sewing room is in the depths of your basement, a light, cheery color, like yellow, pink or light orange, makes a big difference in affecting your mood while you are there. After you are done painting, install a large bulletin board on one wall to help you pin up designs you are working on or pictures that you want to use as inspiration. If you draw your own patterns, a white board or chalk board might also be appropriate.
Good lighting is essential to ensuring you can see what you are doing while you work. Pay attention to the location of windows and, as much as possible, design the layout of the room to take advantage of this natural light. In addition, install several sources of lighting from above and some task lighting over your main work areas. This ensures that everything is lit from more than one direction and helps eliminate the effect of shadows.
The main piece of furniture you need is a desk. If you can afford the splurge, get a sewing desk, which has a recessed area for your sewing machine so you get to work on a flat surface. You also will need a cutting table with a mat to help you measure and protect the table from scratches. One idea for the table is to get a rolling cart so you can store items on the bottom and move the cart away from the wall while you are using it so fabric can hang off on all sides.
The most fun part of designing your sewing room is installing and organizing all of your storage solutions. Start with a set of shelves for your books, patterns, and of course, your fabrics. If you are low on floor space, get wall-mounted shelves to put on the wall above your sewing table or another nearby location. Add a set of drawers to hold the smaller supplies, and label each drawer so you always know what is in it. If needed, get drawer organizers to transform one or more of your drawers into even smaller spaces. If you have other small supplies, such as pins, that you would prefer to not keep in a drawer, get magnetic clear-top containers that you can fill and stick onto to a wall-mounted panel. Store ugly supplies, like your piles of thread, in labeled boxes or bins so you don't have to look at them but know where to find them.