Unless for some reason the moderation system is sending out the default messages despite customization, it should have had a message to the effect that you need to use an appropriate image, and a link to the
guidelines sticky. For a replay, this would be a screenshot of the map during the game, the end-game stats, etc. Random images not related to the upload are not appropriate.
Also strange that you only got it today--the message was sent the day after you posted the replay (Saturday).