Auction items can be handled by using products. However, the complete functionality for auctions is not supported at this time. You will want to set up a product for each auction item. You may want to exclude the product from your events and Shop page so that they do not appear on your public events listing for ticket buyers.
Please note that while you can add these items to your Products, they cannot be bid on since there is not a functionality to manage bids for an auction at this time.