From the Store description:
The best third-party 500px app designed exclusively for Windows 10 Universal. Stay inspired with a continuous feed of the world’s most incredible images, connect with 7 million photographers, and share your best work with a passionate community.
- Share your photos with the world and get recognized by international brands
- Collect photos based on your personal visual style with Galleries
- A unique discovery experience ensures everyone has a chance to get noticed, and keeps you up to date on the latest and greatest from the 500px community
- A sleek home feed will keep you scrolling through inspiring images from the people you follow, and recommendations based on the photos they like
- All photos are displayed uncropped and at the highest quality - your photos have never looked better on a mobile device!
- Automatically updates lock screen/desktop/mobile start screen wallpaper from any Gallery or Photo
A few screenshots of Perfect 500px in action on my Lumia 950 XL:
And the obligatory Continuum shot, proving the UWP app's chops:
Another useful UWP starting point for online services from this developer. You can grab this for free in the Store here.