Alongside a new map set in Widowmaker's family estate in France designed specifically for Deathmatch free-for-all. The two new modes come as part of Overwatch's expanding Arcade Mode, and are both playable now on the Public Test Realm on PC. As per the latest Developer Update video Blizzard has spent time to ensure that these modes aren't simple throwaways.
As highlighted by the new map, and a bunch of modified versions of existing Payload and Capture maps. Another cool feature as part of Team Deathmatch is that Mercy's ultimate ability not only brings back players but also takes away kill counts from the opposing team.
And before you can say, "But Blizzard, you said no Deathmatch for Overwatch", Game Director Jeff Kaplan notes that this was the case until the launch of the Arcade. Which opened up a bunch of different avenues for the team to experiment. And this, according to Jeff, "is just the beginning".