Some of them are things that were present in the old Google+ Photos app and have mysteriously disappeared as of this new incarnation. Others are features we've never seen, but gosh darn it, they'd sure be nice to have.
At the risk of griping about something that's pretty freakin' great, here's my wishlist of elements I'd love to see added -- or added back -- into Google's Photos service:
1. Auto Enhance
One of the coolest parts of Google+ Photos was the fact that it'd automatically enhance any images you uploaded in order to make them look better without any effort on your behalf. You could always dial the enhancements up or down or turn them off entirely if you wanted -- either individually or across your entire collection -- but for most of us, a quick 'n' simple instant tune-up went a long way in improving the quality of our photos.
For reasons unknown, the Auto Enhance feature didn't make it over into the new Google Photos app. You can still edit photos manually one by one, but the magic of having everything improved automatically is M.I.A.
2. Chromecast support
Google's all about the Chromecast, so why did the ability to wirelessly cast images from the Photos app to a TV disappear as of this new version? You've got me. Regardless of the answer, I suspect a lot of us would like it to return.
3. Slideshow support
Described in 2012 as one of Google's "most common requests" for photo app features, the Slideshow command allowed you to launch a nifty moving full-screen gallery of your images from any G+ Photos album. In the new Google Photos, Slideshow is a no-show.
UPDATE: I stand corrected -- there is, in fact, a slideshow option in the new Photos mobile app; it's just in a very weird place where most people (myself included, clearly) would never find it. You first have to open an individual photo in the app, then tap the overflow menu icon in the upper-right corner. There, you'll find an option called Slideshow that starts a slideshow of all the photos in that category or album. Curiously, the option is not present in the more logical place of the photo grid, where you're actually looking at multiple images -- nor is it present at all in the desktop/Web app, where it used to be available.
4. Consistent pinch-based navigation for albums and collections
I love, love, love the way the new Google Photos app (on mobile) lets you pinch in or out to change the photo grid style and navigate into and out of images. But it's confusing that the same capability doesn't carry over into other areas of the app, like albums and collections.
In those areas, pinching does absolutely nothing from the main photo grid. Once you've tapped into a specific album, meanwhile, it'll allow you to navigate into and out of images -- but that's it.
The lack of consistency is confusing, and I'm sure I'm not the only one who's gotten used to pinching in the main photos list and then become befuddled when the same behavior doesn't work everywhere else.
5. An Android widget
Remember when Android used to have a native widget for showing off photos from your personal collection? I'm not sure when that idea went out the window, but it's really strange how no such feature exists for Google Photos. Because man, it'd be great to be able to flip through photos of my daughter right from my home screen. Or at the very least, to be able to quickly pull them up via a home screen shortcut to a specific album or collection.
Widgets have long been one of Android's greatest strengths as a platform. Why wouldn't a high-profile Google app with an obvious visual tie-in take advantage of that option?
6. Co-owned albums
Speaking of tiny yet loud people, my wife and I both take far too many photos of our four-month-old. (And just to clarify, that transition was referencing the baby -- not my wife. Honest.)
I maintain a privately shared album with all of those images both for our friends and family to peruse and for our own organization. Since I'm the only one who can add photos to that album, though, my wife has to periodically send me her images -- and I then have to upload them to my account, add them into the album, and so forth. Not exactly a direct or hassle-free way to accomplish what we need.
If there were a way to assign a co-owner (or "collaborator") of an album, my wife and I would both be able to upload photos from our own devices into the same shared destination. It'd require a bit of permission work, similar to what's done with shared folders in a service like Dropbox or Drive, but I've gotta think it'd be useful for a lot of situations. (A couple other people mentioned the same exact scenario as mine in a discussion on Google+ yesterday, in fact -- and it's easy to imagine plenty of other possibilities where this sort of setup could be relevant.)
So there you have it: my wishlist of features I'd like to see Google add into its new Photos service. And hey, it's early days; maybe some of these things will show up eventually. We can certainly hope.
In the meantime, we've got no shortage of good stuff to keep us busy.