2. The system of claim 1 , wherein the data processing apparatus instructions cause the data processing apparatus to perform operations comprising: determining an image intent score for the search query; and generating an image insertion request when the image intent score exceeds an intent threshold.
4. The system of claim 2 , wherein determining the image intent score for the search query comprises: determining a search property ratio of the search query that is proportional to a number of times the search query was submitted by client devices a search of the image corpus to a number of times that the search query was submitted by client devices for a search of the resource corpus; identifying an explicit intent term in the search query; determining an explicit intent score associated with the explicit intent term; and determining the image intent score from the search property ratio and the explicit intent score.