For one of my images in the "daily life of models" thread I created a twisted pearl necklace. I also tried a version which should work like a piece of cloth. There is a texture given and in MakeHuman I used a aniso-litsphere, but you can easily replace it by different materials (see bump-texture). In the network you will find better shaders for silver etc. as well. The necklace will hover a bit over the character, it is build to fit the evening gown and Mindfront's dresses, so you should apply some corrections in Blender in the end.