Board Thread:Support Requests - Designing Your Wikia/@comment-8334816-20140621200421/@comment-856287-20140622042911

You can't simply make the image size larger; the hi-resolution device will simply detect the size set in the HTML code and then display the image with larger real pixel dimensions.

For example, if you have a Retina MacBook Pro with 2x pixels and a webpage tells it to display the image at "100px by 100px," then it will actually display the image at 200 real pixels by 200 real pixels. If you resize it to "200px by 200px," it won't be nice and crisp, it will just be a 200px image displayed at 400 real pixels by 400 real pixels.

So, how to fix it... I'm not sure how Wikia handles this. I think all you have to do is upload a high-resolution image, and then set the image size in the page lower than the actual resolution. So say you have a 800px by 800px image. Place it on the page with. That will display as 200 real pixels on a normal-res display, and 400 real pixels (2x) on a high-res display. …and up to 800 real pixels on a (4x) system, but any higher (if that ever exists), it would start to get blurry/pixellated. Never mind, apparently you've tried this and it isn't working.

It's possible though, that Wikia hasn't done anything to solve this. I dunno. In MediaWiki 1.21, it's natively supported, but the wiki you linked is running 1.19. That doesn't mean Wikia hasn't already added custom JS to make it serve the proper resolution images.

If all else fails, see what Google has to say about it.