Crop the image when adding a background

[Uranusek]

Is your feature request related to a problem? Please describe. Yes, now some images are ugly stretched or flattened :/

See screenshot

Describe the solution you'd like Ability to select an area on the image when adding a background. Something like that

See screenshots

Use case Adding a background to the keyboard.

Describe alternatives you've considered (if any) Cropping images in a photo editing app, but this may be inconvenient for some people.