Yes, the developers mention it in the recent Live Letter. Their decision was to not implement such a system because of the need to approve every image uploaded. You have to think about the cost on SE for such a feature. The cost of extra man hours. Employee's who will approve/deny the images. Those employee's will need supervisors and managers. You will also have to battle when players dispute their images being denied. SE then would have another means of players getting upset and leaving because they cant have their image.