Hi Michael it's Mark.

In respect to your designer these thumbnails might be looking a little safe. If you need ideas you could look at "Blobchitecture"

https://animalartsdesignstudio.files.wordpress.com/2012/09/jan_kaplicky_tcm20-1554096.jpg
http://architecturenow.co.nz/articles/10-best-examples-of-blobitecture-named/
https://citelighter-cards.s3.amazonaws.com/p17663t05m1rii1r7mj8j1l851up40_61770.jpg

What could work is a marriage between blobchitecture and the modular/organic shapes Phil suggested in your OGR. What about playing with the shapes of his reference images?