Scroll through this link to see if anything catches your interest:
Depends on where the Violin is broken! You could Wire a piece of Dried oasis to it and decorate with Dried Flowers/Leaves etc. and display. You could Paint it Gold or Silver and do the same or just hang up in a music room.
Martine: Why not upcycle with paint and use as a wall decoration? Here are a couple examples:
If you (or a friend) have no artistic talent, then just stripes or simple polka dots might be cute!
My Mom and her Sister mounted my Grandfathers two violins in box frames on velvet and each one got one as a keepsake. I still have Mom's on the wall.
Hang it on the wall as a decor item. Add sheet music and maybe pick up a few other broken instruments as well. Tambourine, drumsticks, harmonica, are some items that pop in my head to add to the arrangement.
Here's some ideas for guitars would work smaller scale for violin http://www.homecrux.com/16-creative-ways-to-recycle-old-guitar-into-beautiful-home-decor-items/79736/
Depends on where the violin is broken, but if you can not tell it is 'broken' by first looking at it, you could attach an unattractive (audio) speaker or radio inside it, then mount the violin on the wall.
What brand label is inside it? Check it's value before you do anything to it to see if it's value justifies restoration or repair or selling to someone for that purpose. If not, the above ideas are all great for decoration use.