LED strip lighting is the most common method since it's flexible and can be cut to length. It's most often found is 5 meter lengths on a roll, but there are specific locations to cut the strip to fit your application. 12 volt and 24 volt rolls are available, but you'll want to skip the 24 volt variety for obvious reasons. If you want to be able to change the color output, you'll need an RGB led strip. If you want white light, you'll need to determine which white color temperature (Kelvin) that looks best to you. Warm yellow light is a 3000K color temp (like old Christmas mini lights). Daylight white light is about 4000 - 5000K (such as most LED running lights in cars).
Without seeing your specific setup, it's hard to determine what is best suited for your application. You can even run polymer fiber (think fiber optics) where the tiny fiber serves as a star in a headliner. Another option is a thin wire (about 1mm wide) that is electroluminescent wire (EL wire for short). This would be useful around small drivers (like a midrange driver for example). EL wire is commonly used in new vehicles as mood lighting around dash and door panels.
There are a lot of options, and a good place to look around is: Superbrightleds.com
