These pictures were taken by me by playing with long exposure and waving around a flashlight in the dark. Of course, if you want to do this yourself, you have to make sure the room is completely dark (except for whatever source of light you're using to 'paint with'), and that you are definitely using a tripod (otherwise everything will end up blurry). This is one of my favorite things to do, because each time, the result is unique.
*photography is mine, shot on Canon EOD 50D DSLR.