You should either update the links to the official WoW art galleries, or remove them, because they no longer work.
Thanks for the heads-up - I've removed the links, as unfortunately I wasn't able to find them at all on any of Blizzard's sites, so I assume they were quietly removed at some point. If they do exist still somewhere, I'd gladly add them back in, as they were excellent places to look for art which fit the style of Hearthstone well.
It's a shame, I liked those galleries. But Pintrest still gets the job done!