Several Shingeki no Kyojin products were released recently and are already at sale in Japan, products like straps, stuffed cushions, rubber magnets, and a lot of different figurines and a large variety of goods. The official website displayed a few promotional pictures of those:
Figurines
Levi's Spin-off
And we have more announced prequels and side stories, as the first season of the anime sees its end, the manga development opens space for several possibilities, Kodansha announced their monthly magazine, Aria, will be publishing a full-scale prequel about Levi "humanity's strongest" at its January issue, there are also plans for more spin-offs at november so we just have to stay tuned for more news and updates.