South Gate Interior
Here's a section of the upper torana in the south gateway interior (the sun has been in an unfavorable place every time I have been there, so I didn't get extensive pictures of this view). This panel clearly shows the past Buddhas, since this segment shows three stupas and three trees (presumably one is missing from the left side of the frame).
The middle torana shows the Chaddanta Jataka, one of five Jataka tales portrayed at Sanchi; another allusion to this story appears on the west gateway exterior. The Jatakas are stories of the Buddha's past lives, usually to illustrate and reinforce some sort of virtue. Chhadanta was a six-tusked elephant king (the multiple tusks are clearly visible in this carving), who lived in the Himalayas with his two wives, and one lesson in the story is the danger of jealousy. One wife became jealous because she thought that Chhadanta preferred her co-wife, and took a vow to be reborn as a princess so that she could get him killed. She was reborn as a princess in Benares, and under the pretext of needing Chhadanta's elephant tusks as a remedy for an illness, she persuaded her husband to hire a hunter to kill him. The hunter shot Chhadanta, who though mortally wounded then helped the hunter saw off his own tusks. The hunter brought the tusks back to the queen, who when she saw them fell down dead from grief. Chhadanta appears four times in this image--once on each side of the central tree, sitting in the lotus flowers at the far left, and alone at the far right, with the hunter right behind him (Mitra 1965: 25).
Here's a close up of the four lion capital motif on the south gate's pillar. This lion quartet was one of King Ashoka's royal symbols, and its presence here testifies to his patronage (and his presence). It is also one of the symbols of modern India, and appears on Indian money (both notes and coins). Ashoka is the paradigm for a righteous king, who conquers by the power of truth (according to Ashoka's inscriptions, he came to this realization only after carrying out a bloody military campaign, in which the deaths and injury filled him with remorse).
Here too you can see (in the lion on the right) that part of the sculpture has been visibly mended.