What you need:
Cover the back of the marble with clear nail varnish OR white glue. I prefer nail varnish because it gives a nice shine, but you can use white glue too.
Sprinkle the top with glitter and leave to dry. Once it's dry, cover with a thin layer of white glue to seal the glitter in.
Simply cover the back of the marble with nail varnish of any colour and leave to dry.
Choose a small illustration and place the marble over the illustration. Draw around the marble and cut the illustration out. Trim illustration until it can fit perfectly on the back of the marble. Take it off and lightly cover the back of the marble with either white glue or nail varnish, and stick the illustration on.
Sorry, not sure what it's called.
Anyway, while the marbles are drying:
Cut a piece of wire about 2.5 inches long. Use the round nose pliers to roll the wire up, like that image over there. Fold it in half so the loops are facing outwards, and use the flat nose pliers to flatten it, so there is no space in between. Hammer it to firm the wire, then use the round nose pliers to roll the long bit in.
You can use white glue or hot glue. It's up to you.
Hot glue dries faster, but makes for an ugly shape.
White glue dries slowly, but is transparent and flat.
If you are using an illustration, remember to stick your hook the right way up (the swirls at the bottom and loop on the top)
Put your chain through the loop and enjoy!