If you continue to post picture after picture, you may see your reach and engagement go down. Why? While it's the most engaging post format, too much of a good thing is bad for your Facebook Page. So try switching up the post formats to increase the chance your audience sees them.
In other formats, make sure that your content is optimized for that post format. Case in point: Don't post a link that has a poor featured image. Since links now pull in large featured images on Facebook, you've got to make sure that featured image actually works and looks okay. Otherwise, your Fans will see something wonky and, most likely, won't click on it, which kinda defeats the whole purpose of posting that link in the first place. So make sure each post format is correctly formatted for the platform.