I don't really count it all that much, because Jim Henson only created the puppets for the program, I don't think he really created anything else.
Back in Season One, he also created the Baker films (especially nice his children got in a few cameo shots).
For Season Two, he created his outstanding Number inserts, which gave him an opportunity to work with different media- stop-motion animation, Scanimate (a very early form of computer animation), etc. Each of these stand as a work of art even outside the context of Sesame Street.
The "12 Rocks in the Desert"- my own fave, and the one that impressed me the most- was even shown at a Yugoslavian film festival and won first prize. Not too shabby.
I've dabbled with stop-motion animation, and it is a painstaking labor-intensive process. But the end results are impressive, so I can appreciate what Jim did for the 12 rocks, Queen of Six, and the King of Eight.