Living legend Bruce Timm quietly joined Twitter back in July, but only in the last couple of weeks has his activity there started to speed up. Never an ardent self-publicist, once upon a time, you had to wait for his art dealer to post his newest sketches and commissions, or else trawl Google Images. Now there's a direct source, and it's flowing quickly. Plenty more examples below.
UPDATE: Apparently this Twitter account isn't actually Timm's. Still, the art is nice.