Besides finding the image of Shulamit's famous letter, I downloaded several other photos from the Hidden History exhibit that may include family members.
First, in happier times in Kovno in the 1930s, here is a group of Jewish schoolteachers at a social gathering. Our great-great aunt, Bluma Rabinovich, the younger sister of our great grandfather Joseph Rabinowitz, was a schoolteacher in Kovno at that time. Quite possibly she is one of the women in the picture. (The photo credit is "In Memory of Shalom Zvi Rachkovsky.")
Here, undated, is a photo of Kovno's Jewish Council. The caption tells us that chairman Dr. Elkhanan Elkes is seated third from left and vice-chairman Leib Garfunkel is seated at far left. Is it possible that Shmuel's father Yitzhak Rabinovich is one of the other men in the picture?
The credit on this photo is "Avraham and Pnina Tory, Israel. Photograph by George Kadish, Beth Hatefutsoth, Israel." Avraham Tory was the leader of the community that spearheaded efforts to archive historical documents from Kovno. He managed to bury three crates of artifacts, including the photos by documentarian Kadish, two of which he was able to recover after the war.
On both these questions, our upcoming call with Shmuel should clear up whether our Rabinowitz family members are among those in the photos.