Board Thread:Support Requests - Designing Your Wikia/@comment-1647694-20151207020241/@comment-4731443-20151207032736

Images are automatically resized for mobile. That's why they won't look right if you visit the page using the wikiamobile skin but not resizing your window to cellphone screen size; when you do that they expand for your screen size, but using the downsized image as a basis, which results in poor quality.

Below is the URL for the deer picture when viewed on the mobile skin. Notice the cropping and resizing parameters in bold:
 * http://vignette1.wikia.nocookie.net/intothelongdark/images/3/3c/Deer_Running.jpg/revision/latest/ window-crop/width/200/x-offset/0/y-offset/11/window-width/979/window-height/979?cb=20151119203846

If you use Firefox, you can turn on Responsive Design View (Crtl+Shift+M) to generate a page within a smaller frame without resizing your actual window.