All cover artwork entries currently link to 250px and 500px images. This includes images that were uploaded at 250px or less. For these images, the 250px image and 500px image are identical to the original image. These links are present even if the uploaded image file is smaller than either 250px or 500px - giving the false impression that you're getting a different or larger image by clicking on one of those links.

Images which aren't at least 500px shouldn't have a 500px link on the cover art page, and images that aren't 250px shouldn't have a 250px link on the cover art page.

(NOTE: The actual URLs shouldn't be removed, just the links on the image in the Cover Art tab of the release page)

For example:

On the page:
http://musicbrainz.org/release/ad7a42c2-8baa-4f6c-8d71-1ae2f7cf3afa/cover-art

There are links to these three images:
"original": http://coverartarchive.org/release/ad7a42c2-8baa-4f6c-8d71-1ae2f7cf3afa/2361226738.jpg
"250px": http://coverartarchive.org/release/ad7a42c2-8baa-4f6c-8d71-1ae2f7cf3afa/2361226738-250.jpg
"500px": http://coverartarchive.org/release/ad7a42c2-8baa-4f6c-8d71-1ae2f7cf3afa/2361226738-500.jpg

In this case, "250px" and "500px" should not be shown, as they don't point to images of a sufficient resolution.