The release of the the December Issue 2020 (released on October 26th) of Monthly Shounen Sirius contained four new character designs for
Tensei Shitara Slime Datta Ken 2nd Season.
The new character designs are for the characters (right to left, top to bottom) Hinata Sakaguchi, Shougo Taguchi, Kirara Mizutani and Kyouya Tachibana.
Of the four characters, only Hinata Sakaguchi had a cameo appearance in the first season of the series so far, although she has not said anything in the first season of the series and hence her Voice Actress is still unknown. Regarding the VAs, we might get more information on the "Tensura Youtube Livestream Event" on November 8th, which is also said to provide us with a new trailer.