Such drawings are not authentic at all and never reflect the real image of the Infallible Imams (AS). It is wrong to call it picture because picture reflects the real shape like a mirror or near to it. Such drawings are not pictures but just imaginations of the persons who drew it based on his knowledge and culture.
It might be accepted in some cultures to draw such imagination drawings of the Infallible Imams but in ,any other cultures it is not accepted and it might cause some persons feel disrespect for the Infallible.
It is wrong to claim that these drawings are real pictures of the Imam and such claim can amount to lying on the Imam.
Millions of Shia Muslims do not have such drawings as it is linked with a cultural factor existing only in some counties and not all Shia Muslims have the same culture in this regard. All Shia scholars say that it is wrong to claim that such drawings represent the real shape of the Imams.
Even Sunni Muslims have drawings of their leaders like Abu Bakr and Omar as you can see it in some museums in Turkey. It is a matter of culture and not a part of religion.