Here are some projects I found:
Wow, love the marble ball fence idea.
You can glue to glass panes and objects to make a marble stain glass affect. You can glue to any object to embellish. You can embed them into wet concrete stepping stones, create a design or words. Add to the bottom of a glass vase, or aquarium they look great under water.
Dorie: Maybe these will help
Here are some more ideas! https://wonderfuldiy.com/colorful-creative-crafts-using-marbles/