Unlike champions in various MOBAs, StarCraft units don't have any skins or any cosmetic features, so we have to compensate with our imagination. Artist Tamás Gyerman, for example, took a few units from the game and redesigned them to fit a post-apocalyptic world.
The latest, at the top, is a giant mecha, or even steampunk version of a Zerg Baneling, possibly still able to burrow or explode. Here's two more below from the same artist. The Terran's high-speed buggy, the Hellion, and a Vulture, a classic Brood War unit. They're all really cool, I'd absolutely play a special Terran vs Zerg on a map like this.
Check out Gyerman's gallery on DeviantART for more.