This site is full of craft ideas for you to make
Here are some more marbles I have created using the faux effect I described in detail on this site.
This was painted on wood using gloss paint which madethe paint easy to spread around.
In stead of 4 layers I tried 9 layers and all done with a splatter brush to get a much grainier texture
With this one, rather than inventing the lines I actually copied a real piece of marble. There are 20 layers here so it took 2 weeks, but the result was really pleasing.