Self note
Scenario: Getting reports saying most of Wordpress images ERROR 404. In fact, they are exists in /wp-content/uploads/* folders.
Solutions:
Failed — Disabled certain plugins, disabled all plugins, change uploads folder/files permission, modify .htaccess file, delete .htaccess file, change Permalinks settings to default, etc
Success — Switched the PHP Date Format in General Settings from Custom (D, M jS, Y) to Default F j, Y (e.g: August 10, 2015)
