While there aren't as many improvements compared to iOS 11's Photos additions, the tabs menu in Apple's updated Photos app for iOS 12 was revamped to include "Memories" inside a new "For You" tab that also houses featured photos and effects suggestions. This is also where you see sharing suggestions and all of the albums others have shared with you.
Whether you mean to or not, taking burst photos is super easy on the iPhone. In the Camera app, just compose your photo, tap-and-hold the shutter button, and watch the number of pics go up and up until you take your finger off the screen. However, finding that one special keeper out of all of them in the Photos app isn't as intuitive as taking them in the first place.
While it may not be an obvious feature, Apple actually built a way into iOS that lets you hide specific pictures and videos in the Photos app that you want to keep on the down-low, for your eyes only. If you show off your photos a lot or stream slideshows to your TV, this is a great way to keep less appealing content private.