Dropbox's Carouselapp will soon help you reclaim space on your device. The app will also make it easier to browse through your older photos with the new Flashback feature.
Carousel will allow you to free space on your device when it's running low by removing photos and videos from your device that are already stored in Dropbox. Tap the app's notification that warns you about low space, and you'll be taken to a page that shows you how much space can be regained by deleting photos and videos. Finally, tap the button to free up space. This feature will also available through the app's settings.
Flashback is a new way to surface older photos. Go to Settings in Carousel and select Flashback in order to use it. Select a time period, such as one or two years ago, and scroll through your photos from that time. Flashback isn't ready for release just yet, but should be making its way to iOS soon.