What follows are answers given to the above question by the religious authorities (grand jurists):

Grand Ayatollah Khamenei (may Allah grant him long life):

As per the Islamic law, there is no problem in it by itself provided that it is not considered desecrating or disrespectful according to Urf (custom) and that it is not opposed to the status of the Imams.[1]

Grand Ayatollah Saafi Gulpaigani (may Allah grant him long life):

Generally speaking, to avoid hanging those portraits [on walls] is more suitable with the status of the noble Imams.

Grand Ayatollah Fazel Lankarani (may Allah bless him):  

There is no objection in it, although there is no validity in ascribing them to the Infallibles, peace be upon them.

Grand Ayatollah Bahjat (may Allah grant him long life):

It is not free of objection.

Grand Ayatollah Makarem Shirazi (may Allah grant him long life):

These are not real pictures. However, since they are ascribed to the Imams (a.s), they should not be disrespected.

Grand Ayatollah Sistani (may Allah grant him long life):

If it does not involve desecration of them, there is no problem.

Grand Ayatollah Tabrizi (may Allah bless him):  

If they are meant to remind people of those noble leaders, there would be no objection; but if one takes these pictures for real pictures of the Imams, peace be upon them, such a belief is erroneous and false.[2]