I've been banging my head on that one for a fex days now!
Basically clean urls test fails in admin/config/search/clean-urls which I assume is normal in a nginx environment (?)
No biggy as I force it in setting.php
When clean urls are turned on everything works as expected but image styles.
images are getting uploaded in sites/default/files as one would expect, but are not being generated when I visit the page.
My assumption is that something is broken with clean urls.
So the question is do you guys pass the clean urls test in admin/config/search/clean-urls with nginx?