Displaying the image in Power Apps itself is not difficult.

Usually, you just need to set the Image property to the image URL:

In a gallery, it will be limilar, something like ThisItem.Thumbnail.Large.

If you are working with public web images, it will work without any issues. However, if the image is stored on OneDrive or SharePoint (and it often is), it might not display. Sometimes the image is visible on Windows in a regular browser only, but it is not visible when running the app on Android or iOS. This is because Android and iOS handle image permissions differently.

The solution is to connect a document library as a data source for the app and then reference it.

Connection of library

Here’s how to connect a document library:

We can display it in a gallery for clarity, but it’s not necessary.

Displaying in image

In the image itself, you can then query the data source using a function such as Lookup.

It’s not difficult, but one disadvantage could be that if the library contains more than 2000 records, there might be a problem with delegation.