It's because of a too strong Email Address Obfuscation service of CloudFlare that interferes with @ characters in inline CSS. Some CSS has @, for example media queries and retina-ready file names that contain @2x text. JIG uses those for the magnifier icon on the thumbnails. Some presets include the magnifier icon and that in turn includes CSS susceptible to alteration by CloudFlare. It becomes invalid CSS and any rules after that become unused. Including rules that manage the proper layout.
- Go to your CloudFlare settings.
- Click Scrape Shield - the last button on the top.
- Turn off the Email Address Obfuscation.
While JIG is compatible with CloudFlare, there are a few extras that mess too much with the code. This feature is one of those. Furthermore, in most cases it's not recommended nor possible to use CloudFlare Rocket Loader™ with JIG either. None of which are enabled by default.