1. A method comprising: generating a plurality of model-generated scores; wherein each model-generated score of the plurality of model-generated scores corresponds to a candidate image from a plurality of candidate images for a particular video item; wherein generating the plurality of model-generated scores includes, for each candidate image of the plurality of candidate images, feeding a set of input parameter values into a trained machine learning engine to produce the model-generated score that corresponds to the candidate image; establishing a ranking of the candidate images for the particular video item based, at least in part, on the model-generated scores that correspond to the candidate images; selecting a candidate image, from the plurality of candidate images, as a representative image for the video item based, at least in part, on the ranking; wherein the method is performed by one or more computing devices.