There is a new post-apocalyptic, steam-punk themed anime this Spring, and it's probably exactly what you need if you're hankering for a new season of Attack on Titan. That anime is called Kabaneri of the Iron Fortress.
Attack on Titan's long-awaited season 2 has only seen more and more delays and push backs. It was originally believed that AOT's season 2 would be a springtime 2016 release (i.e. now) but that has proven to be untrue.
Some people think that some of the delay in AOT's season 2 could be tied to the new anime from Wit Studio, Kabaneri of the Iron Fortress. Wit is the animation studio that has done Seraph of the End, Rolling Girls, and Attack on Titan. With this latest foray into apocalyptic fiction, Wit has certainly type-casted itself, but so far the new series is meeting critical acclaim.
Kabaneri of the Iron Fortress (or Koutetsujou no Kabaneri) is an anime set in a world that has been ravaged by large and almost super-powered zombie-like beings called Kabane. The few survivors left in the world hide in fortified railway stations or travel around in an iron-clad train - the Iron Fortress, probably. The aesthetic of the show is straight up steampunk, with plenty of pipes and bronze and characters tinkering with scrap.
I've only watched the first episode myself sor far, but I think it's promising. The animation is fluid and vibrant like we expect from Wit, but it also has something about it that hearkens to the steampunk progenitors like Steamboy and Arcadia of My Youth. The action is intense and the atmosphere is, too. Within the first few minutes of the first episode, a man kills himself after being bitten by one of the Kabane so as to protect the people of the train and to save his friends from having to kill him themselves.
It just started on April 8 and two episodes are available (as far as I know). If you are a fan of Attack on Titan, or a fan or action-based steampunk anime, you should definitely check this one out.