what u need is just
I [1] I an old necklace or just have a look in a building supplies store [department bathroom accessories]
there is a wide choise of chains I [2] I polystyrene paper 5mm - take 2 colors: e.g. black&white I [3] I cutter
now sharpen your pencil and draw your motive on the paper I
next cut it out I pierce a small hole through the top of your motive and fix your necklace