I have sold relatively low value furniture & ornaments at auction.
It's relatively expensive in sales costs, paying auctioneer fees, and a %age if sales price. Make sure you know what proportion of the price you will actually receive.
Choose your auction wisely - make sure they deal in the kind of stuff your selling. If it's worth 2million, don't sell somewhere that attracts car-boot sale fanatics, and vice-versa.
Check for insurance - at what point is it covered by the auction house (or new owner), and is there a gap between when your insurance ceases to cover it and someone else's starts?
Ask the auctioneers advice, and tell them anything about the item that would make it more appealing or valuable.
If it's something really obscure, then youd be better selling online.
It's much easier than selling direct to buyers, if less profitable! Theres no concern about no-shows, aggressive haggling, and its quicker.