UWP apps (or Windows Store apps, or apps in what's called sometimes the "AppX application model") information can be queried from official APIs.

These APIs don't have a C# equivalent AFAIK but I've provided sample code to do this in my answer to a similar question here on SO: Getting icon of “modern” Windows app from a desktop application?

The sample application dumps all current loaded Windows Store packages & apps.

Note there is not just one icon for a UWP app, there may be many, to be able to adapt to a specific device, form factors, etc. The sample code has a utility that gets the highest scale image for a given resource.