I just had my basement renovated last year and I'm so happy with it!
It was one of those nasty cinderblock basements, dark and dingy. There are 3 small windows on the east side and none on the west side, so lighting was definitely a consideration.
I wanted a family room/playroom area, a full bathroom and a gym area.
The contractor who renovated one of my bathrooms said he could do the whole job excluding electric. The goal was to keep it under $20K, which is cheap for this area. I drew up a layout for him and for the electricians, based on some helpful information I was able to get from the web (I downloaded a booklet on renovating basements for about $17 and it was probably the best $17 I spent).
Because of the low natural lighting, I kept the floor plan very open. We put walls up with access doors to block off the furnace/hot water heater/water tank/oil tank (furnace required louvered doors for airflow). We also walled off the laundry area and put in double doors for easy access, but left that area unfinished. The only other areas we walled off were a large walk-in storage closet and the bathroom. Everything else is open, including the staircase. This made the whole basement seem more airy and light and gives the impression of being a bigger space than it really is.
For lighting we used high-hats and accent sconces. It never feels unnaturally dark.
The contractor sealed up the cinderblock walls with special paint that helps seal out moisture (however, very important to deal with any leak issues before you have major work done. I redirected my downspouts and clean my gutters out 2x a year to prevent basement leaks). Then he sheetrocked the walls, about 6 inches away from the cinderblocks (again, to prevent leaks and mold). He also sheetrocked most of the ceiling, except one part where there are too many pipes - in that section we did a drop ceiling for easy access to plumbing. He did have to leave some exposed pipes/heating ducts in a few areas, but I hardly even notice them. It's amazing how polished everything looks with the sheetrocking.
We painted the walls cottage white with white floor and ceiling trim. I originally wanted carpeting on the floor, but a friend talked me out of it and I went with a pine laminate over a vapor barrier instead. It looks fantastic and is so easy to clean. I finished off the whole look with a big screen TV, area rugs and a very nice futon. There are storage shelves in the gym area for all my son's toys. I still can't get over the transformation!
Just remember to test for radon before beginning your project. Once it's done, you'll need to invest in a good humidifier to keep out the damp. I also put one of those plug-in scent things down there.
Sorry this is so long, but I'm still excited about it! Best of luck!