I've found a side view of the cup, showing both a clear view of the walking stick as well as the object behind. This appears to me to be a column with a statue of a woman on top. Hard to say what's at the base of the column, or who the woman (goddess?) is.
A more interesting question for me was the walking stick itself, as well as the bags carried by the philosophers. It seems that this represents the "wallet and staff" that marked out Cynicism, but was also a generic symbol for Greek philosophers.