Find open source virtual backgrounds at the following resources:
Virtual background tips:
An easy and quick way to create a high-quality image for your virtual background is to adjust the aspect ratio of any template to 1280 x 720 pixels and add, remove and customize elements to your liking.
These image resources are created under either a completely unrestricted use license, or a Creative Commons Zero (CC0) license, meaning that you can download, use, manipulate, share, distribute, or otherwise use them for whatever purpose you'd like without permission. It is strongly recommended that you credit the creator(s) of the image, but it is not necessary.