Talked about backup plugins. Good list here:
http://www.wpbeginner.com/plugins/7-best-wordpress-backup-plugins-compared-pros-and-cons/
Images
Media files: 4.4 uses responsive images
https://developers.google.com/speed/webp
Ron had a problem that seems to be addressed here: http://support.advancedcustomfields.com/forums/topic/repeater-field-with-image-type-wont-update-if-image-too-small/
SEO
https://moz.com/beginners-guide-to-seo
Yoast
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=rand+fishkin&tbm=vid
https://duckduckgo.com/