AreaLight
works only with WebGLDeferredRenderer
, which is quite new, part of the examples (not the library), and there are not a lot of examples of it's use.
If you look at this example, you can see a movie texture is used as a light source.
In this example, you can substitute another texture for the video texture like so:
// texture = new THREE.Texture( video );
texture = THREE.ImageUtils.loadTexture( "texture.jpg" );
Unfortunately, this example is using a modified version of the library.
three.js r.56