Crates are the running gag of the video game industry. They're over-used, visually boring and frankly, the cheap way out for designers who don't want to come up with more interesting breakable objects (and artists too lazy to make more complex shapes) - they are handy for jumping on, but what do you do if you break the crate underneath?
Old Man Murray came up with a review system they call "Start to Crate" - the time it takes for a player to encounter a crate from the start of the game. It's a brilliant idea and a good gauge to set your game against for just how creative it is.
Rather than re-invent the crate... er wheel, here is a list of fifty breakable objects you can populate your game with other than the humble (and boring) crate:
Barrel, Treasure chest, Vase, Urn, Garbage can, Mail box, Metal drum, Cargo container, Cardboard box, Cage, Lantern, Light fixture, Desk, Filing cabinet, Fish tank, Toy box, Keg (or cask), Hay bale, Pile of skulls, Dog house, bird house, Idol, Statue, Fortune teller machine, Church donation (Alms) box, Suggestion box, ATM, Hollow tree stump, Log, Attache case, Suitcase, TV or computer monitor, Fuel tank, Refrigerator, Oven, Breadbox, Cabinet, Wardrobe, Parked car trunk, Crypt, Sarcophagus, Coffin, Video game console, Soda machine, Vending machine, Oxygen cannister, Filled shopping cart, One-armed bandit (slot machine), Copy machine and Toilet.
Just make sure you use a little creativity when thinking of these things. Use the crate only as a last resort.