My sorority does this thing with our new members where they take big rocks and decorate them for active members and we use them to hold our doors open and what not. I just use them as decorations because they're so freaking cute! So two girls decorated rocks for me :)
You don't need to be in a sorority to do this (obviously). I just Wanted to put the idea out there that you CAN use rocks as decorations, you just need to get creative :) They look good on desks, or you can use them to hold your books up on your shelf!