What is the average number of movies added to the lists of user 8516503? Give the user profile image URL on Mubi.
user profile image URL refers to user_avatar_image_url; user 8516503 refers to user_id; Average refers to AVG(list_movie_number where user_id = 8516503)


SELECT AVG(T1.list_movie_number), T2.user_avatar_image_url FROM lists AS T1 INNER JOIN lists_users AS T2 ON T1.list_id = T2.list_id AND T1.user_id = T2.user_id WHERE T2.user_id = 8516503
database name:db_id movie_platform
lists table lists Cols: user_id dtype integer, list_id dtype integer, list_title dtype text, list_movie_number dtype integer, list_update_timestamp_utc dtype text, list_creation_timestamp_utc dtype text, list_followers dtype integer, list_url dtype text, list_comments dtype integer, list_description dtype text, list_cover_image_url dtype text, list_first_image_url dtype text, list_second_image_url dtype text, list_third_image_url dtype text, 
movies table movies Cols: movie_id dtype integer, movie_title dtype text, movie_release_year dtype integer, movie_url dtype text, movie_title_language dtype text, movie_popularity dtype integer, movie_image_url dtype text, director_id dtype text, director_name dtype text, director_url dtype text, 
ratings_users table ratings_users Cols: user_id dtype integer, rating_date_utc dtype text, user_trialist dtype integer, user_subscriber dtype integer, user_avatar_image_url dtype text, user_cover_image_url dtype text, user_eligible_for_trial dtype integer, user_has_payment_method dtype integer, 
lists_users table lists_users Cols: user_id dtype integer, list_id dtype integer, list_update_date_utc dtype text, list_creation_date_utc dtype text, user_trialist dtype integer, user_subscriber dtype integer, user_avatar_image_url dtype text, user_cover_image_url dtype text, user_eligible_for_trial dtype text, user_has_payment_method dtype text, 
ratings table ratings Cols: movie_id dtype integer, rating_id dtype integer, rating_url dtype text, rating_score dtype integer, rating_timestamp_utc dtype text, critic dtype text, critic_likes dtype integer, critic_comments dtype integer, user_id dtype integer, user_trialist dtype integer, user_subscriber dtype integer, user_eligible_for_trial dtype integer, user_has_payment_method dtype integer, 
