I think that would open the door to a number of unfortunate consequences. We know that people sometimes use heuristic indicia and shortcuts when they vote, in particular in some less important elections, like municipal votes.
The mere alphabetical order of the candidates can already have consequences at the municipal and national levels. The presence of images or photographs of the candidates could certainly open the door to unfortunate consequences.
That is not a firm and final opinion, but it is what comes to my mind when I'm asked the question.