Yellowjacket has gone through many changes in the comics. First Yellowjacket was Hank Pym, then Rita DeMara, then even Ultron when it came to the Earth-1610 version. In the upcoming film, Yellowjacket will be played by actor Corey Stoll. Stoll has said that his character is the protégé of Hank Pym who eventually gets ahold of a next-gen Ant-Man costume. Well this pic below, which popped up on the MovieBook Twitter page, may be the first look of Yellowjacket.
MovieBook suggest that it is our first look at Yellowjacket.