I created very early in the cycle a spreadsheet (https://docs.google.com/spreadsheets/d/10ZVKVyim4vpep-uO9zhegyiv2Ld41vupFgB8d37o0kY/edit#gid=0) with some 'fallback' images that could be used.

Unsplash was used as Martin Wimpress has blogged (numerous times) how it's the fallback for Ubuntu-MATE as a compatible license is available for most images. All images appeared compatible (at time of adding to gdoc-sheet anyway)

In *impish* a user on the forum offered some created wallpapers which was perfect timing.. we may not always be so lucky; so are these suitable? more needed? or are we in need of something?