Why is the Imam's Photograph Being kept in the Jamatkhana? Isn't this Idolatry?

This question has already been answered by an eminent contemporary Ismaili scholar:

The answer to this question is that [to revere] the blessed picture of the Imam is never idolatry, for the Imam is the living supreme Name of God, which is “al-Hayy al-Qayyum” (the Everliving and the Everlasting). 

The picture is a symbol and sign of this supreme Name, just as Allah is the name of God, the letters of which alif, lam, lam and ha are by no means God Himself, but are only symbols and signs through which the name of God is determined and recognized. Therefore, neither the letters nor the word “Allah” is meaningless. Thus, the sense in which the blessed personality of the true Imam is the supreme Name of God, so in the same sense, his picture is the supreme naqsh (the written form) of God.

The obligatory pilgrimage (Hajj) is one of the seven pillars of Islam. If its rites are looked at from the exoteric point of view, many of them seem to be like idolatry. But in reality they are not so, because God and the Prophet have kept numerous ta’wili wisdoms in them.

In the wise Qur’an in verses (2:158; 5:2; 22:32, 36) are mentioned the "symbols of God" (sha'a'iru’llah), the respect and reverence to which is regarded as the righteousness of the heart. It is crystal clear that the personality of the Prophet and the Imam is itself from among the symbols of God. Had it not been so, then the Prophet would not have said: “Whosoever saw me, saw God.” Further, the Prophet would not have said: “To look at the countenance of 'Ali is worship ('ibadat)”; “To look at the Qur’an is worship”; and “To look at the Imam is worship.” From all these sayings it is evident that the personality of the Prophet and the Imam is from among the symbols of God, and therefore the picture of the Imam of the time is worthy of respect and veneration.

– 'Allamah Nasir al-Din Nasir Hunzai, One Hundred Questions, 61.

Additionally, after the conquest of Mecca, the Prophet found there to be paintings of Abraham, Mary, and Jesus in the Ka'bah along with the many other paintings and statues of numerous pagan deities. He had all the pagan ones destroyed but protected the ones of Abraham, Mary and Jesus from destruction:

Apart from the icon of the Virgin Mary and the child Jesus, and a painting of an old man, said to be Abraham, the walls inside [Kaaba] had been covered with pictures of pagan deities. Placing his hand protectively over the icon, the Prophet told 'Uthman to see that all other paintings, except that of Abraham, were effaced.

– Martin Lings, Muhammad: His Life Based on the Earliest Sources, 300 (ref.: al-Waqidi, Kitab al-Maghazi, 834, and Azraqi, Akhbar Makkah vol. 1, p. 107)