Ran into an issue when trying to upload files of size > 1MB.
In order to allow bigger uploads one has to modify the nginx config (/apps/www/sites.d/grav.conf.tpl) to contain client_max_body_size 64M; and modify the php config to contain config upload_max_filesize = 64M.
It would be nice to have a config option to set those when starting the container (or maybe have a somewhat more permissive default of > 1MB?).
Of course it is still possible to fork the image and have the modified config files in place as workaround.