A recent news post on the official MultiVersus website confirms that Looney Tunes antagonist Marvin the Martian will be joining the star-studded cast of playable characters at some point during Season 2. No specific release window was given on when he'd be available; it was simply stated that he'd "soon be making his way to MultiVersus." The post also states, "We'll have more information about Marvin and his kit soon, so hang in there!"
A new Game of Thrones stage will be coming at some point as well, and it's said to have "all the hazards and pitfalls you’d come to expect from the land of Westeros." It's unknown what these hazards will be. The news post gave no further info about the stage, aside from the following image. Given what it shows, it could be that this is another stage where players can walk from one end of it to the other, much like the recently added Space Jam map. The image could, however, just be the stage's background, so we'll have to wait and see.
The news post also mentions said Space Jam map, with the announcement that it will now be available in other modes outside of custom and lab games. The main gimmick of this map is a basketball that can be used as a projectile. The post reads, "Introducing maps with unique features is so much fun for us and the Space Jam map is just the beginning of what we have in the works." So, it could be that this new Game of Thrones stage could house some other form of game-changing hazard that's more impactful than the traditional obstacles that simply deal damage.
The Game of Thrones map is also said to feature an "all-new remix" of the iconic HBO show intro song. It's stated that it will contain multiple varying sections that will change seamlessly depending on what's happening in the match. Likely a very welcome addition for fans, as one of the game's recurring criticisms has been its lackluster soundtrack, which is especially disappointing given the wealth of IP it has at its disposal.
Marvin the Martian first appeared all the way back in 1948 and has had numerous clashes with Bugs Bunny since. He uses various gadgets and weapons in his attempts to destroy the earth, which he does because, according to him, it blocks his view of Venus. In the end though, he's always foiled by Bugs. With that being said, it's likely for him to be a Mage/Ranged character that uses gadgets to deal damage from afar.