File talk:other car.jpg
The (an?) issue with the original JPEG image is that it's clockwise rotated 90 degrees compared to the image as displayed on xkcd.com, as can be seen by using your browser to view the image itself (which is the "hotlinking" URL http://imgs.xkcd.com/comics/other_car.jpg ). However I cannot see why my browser (Chrome), and presumably everyone else's, displays the image correctly in the xkcd web page.
Specifically the web page contains no significant differences from another that displays a JPEG (as compared to a PNG, not that that probably matters anyway), such as 267: Choices: Part 4. In fact, Chrome displays the correct image with the simplest web page to display an image (<html><body><img src='http://imgs.xkcd.com/comics/other_car.jpg'/></body></html>) even though that otherwise seems to correspond to what displaying the image directly corresponds to.
I note the metadata of the image, as uploaded here, says "Orientation: Rotated 90° CCW". Perhaps browsers notice that automatically in most situations...
I have enabled "external" hotlinking to this wiki's images and that shows this image displays fine when displayed directly, but the thumbnail image is always being displayed and never generated :-( See my sandbox. Mark Hurd (talk) 14:23, 21 April 2013 (UTC)
User:Daddy's upload fixed the issue that the wiki was always using the thumbnail version. Note the thumbnail versions still fail.
I have disabled the "hotlinking" feature again.