If you need a PNG with a transparent background on an image you can checkout Transparency Capture for unity. It works quite well but needs a little set up.
This is what the description from the Unity store says "With Transparency Capture, you can save screen shots (not include GUI) as PNG file without background color, and the screen shot can even include transparency (alpha value) from scene objects. "
I have been using this to create thumbnails for items in unity. One could also make promotional images for media kits if they needed.
I go through the creation of one image. Where to get the add on. importing it, setting up a scene, staging it for the shot and where the PNG image will be stored.
Transparency Capture
https://assetstore.unity.com/packages...
Created by Oragne030
Intro Song:
From The Dust - Alive [Creative Commons]
Release: / from-. .
License: http://bit.ly/CCAttribution
A Creative Commons Attribution License (CC BY) states that the material can be shared, remixed and used commercially as long as you give appropriate credit.