I used to buy a lot of WB art, mostly the Model Sheets. It helped that I was working at one of the Studio Stores at the time and got a 20% discount. My favourite (and first) buy was the Batman Lightning cel which I've had for about 8 years now and still love and has appreciated nicely in price. At the end of the day I was buying because I liked and if that's the attitude you stick with you shouldn't be disappointed.

One cel I always regret not buying was a 1/1 where they'd taken a scene from a Wile cartoon The Fast and the Furyous which they'd managed to match the original pencil drawing to. The scene was quite comical but I couldn't afford the £1200 price tag. I wonder where that is now.