I've purchased some flat, white boxes at a Party Supply Store for under a $1.00 each. They fold-up to make cubes and come in a variety of sizes. They can be decorated very easily to go along with your theme and you can also cut a thin rectangle on the top flap with an exacto knife to create a slit for your tickets. They also look really cute when you add round circles to make your box look like dice!
I also love using fun items that go with the theme. For example, use plastic coconuts or pineapples for a Luau theme. Use treasure chests for a pirate theme. Plastic apples are cute and can be used year around. The plastic fruit has a top and a bottom, and most have a small circle in the top for a straw. These kinds of ticket holders add to the whimsey of the event and really last forever.
I also like to remind people why we are there. One year I used cardboard books for our boxes when we were fundraising for our library. They can be decorated, and come in a variety of sizes with plenty of room inside. If you decorate these books with your school's logo, you can use them year around.