"Here’s what iCloud backs up: Photos and videos on your iOS devices, unless you turn on iCloud Photo Library on your iOS device (iOS 8.1 or later)."
https://support.apple.com/kb/PH12519?locale=en_US
The photos hit the same 5 GB limit, so it's not like excluding or including them really changes anything. Photos are the #1 reason people hit the backup limit.