Flickr is the world's most popular image sharing site and provides us with 1 TB of space per account. This app developed with flickr API, android studio 3 and build tools 27, design with interactive and responsive user interface, smooth material design guidelines from Google, latest version of Android Oreo and P supported. The app is fully finished, but if you want, you can customize and add more features. You can save money and time by using this app.

1. User Authentication: Allow users to sign in with their Flickr accounts. This will enable them to access their own photos and interact with the Flickr community.

2. Search and Explore: Implement a search feature that lets users search for wallpapers based on keywords, tags, or categories. You can use the Flickr API's search endpoints for this.

3. Trending and Popular: Showcase popular and trending photos on Flickr to help users discover new wallpapers. You can use Flickr's interestingness and trending endpoints for this.

4. User Collections: Allow users to create collections of their favorite wallpapers. They can save and organize their preferred photos in one place.

5. Set as Wallpaper: Provide an option for users to set the selected image as their device wallpaper directly from your app.

6. Download Images: Enable users to download wallpapers to their device for offline use.

7. Favorites and Likes: Allow users to like or favorite images, and also see their own liked images.

8. User Profile: Display user profiles, showcasing their uploads, favorites, and collections.

9. Comments and Discussions: Allow users to view and participate in discussions and comments on photos.

10. Notification System: Implement push notifications for when a user's favorite photographers or collections are updated.

11. Settings and Customization: Let users customize aspects like image quality, download location, and update frequency for trending wallpapers.

12. Offline Mode: Implement the ability to access previously downloaded wallpapers even when offline.

13. Filters and Sorting: Provide options for users to filter and sort search results, such as by date, popularity, or relevance.

14. Share Images: Enable users to share their favorite images with others through various social media platforms and messaging apps.

15. Ads and Monetization: Consider integrating ads to generate revenue, or offer a premium, ad-free version of the app.

16. Feedback and Reporting: Include a feature for users to provide feedback and report inappropriate content.

17. Analytics: Integrate analytics tools to track user behavior, such as which images are popular or how often users set images as wallpapers.

18. Permissions and Privacy: Ensure that you ask for the necessary permissions and inform users about how their data will be used. Implement strong privacy measures.

19. Dark Mode: Support both light and dark themes for the app.

20. Tablet and Multiple Screen Support: Make sure the app is responsive and works well on various Android device screen sizes.