Whizbang Dustyboots
Gnometown Hero
Tossing already-seen art on a t-shirt with your logo in the corner isn't creative or compelling. It's lazy. Even those of us who love the old box art aren't likely to buy more than one t-shirt like that, and given how many companies are just trying to sell shirts with the same handful of licensed art on them, it's a problem.
And worse for WotC, this actually encourages would-be customers to go to Etsy or RedBubble or other places where non-licensed art is being used and WotC gets no money at all (although they obviously benefit from the brand recognition). If you want to better monetize the brand, start with making licensed merchandising more worth buying.