Can I retrieve accidentally deleted SMS messages and photos?

If you're using iCloud Syncing for Messages, messages are not part of your back up. Once you delete them, they're gone.

If you're not using iCloud Syncing and you have a back up that contains the messages, you can restore your phone from that back up.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Note that doing so will overwrite everything currently on the phone.

Do you have a backup of the phone made when they were still present?