Google Meet backgrounds
At the time of writing, Google has announced that soon you will be able to customise your background within Google Meet.
However it is possible to do it now using a free third party extension for Google Chrome.
Visual Effects for Google Meet has a Virtual Green Screen feature as well as Blur, Pixelate, Inverse and Contrast features
You can install it directly from the Google Chrome store
Install from Google Chrome store
or visit its home page here for more details
Visual Effects for Google Meet home page