Steps to replicate the issue (include links if applicable):

• Choose an image with a width of 12000 pixels at commons
• click on any of the thumb links (for example "300px"
• replace the thumb size in the URL with "7680px"

What happens?:

The browser will display a 500 http status page

MW does never create a thumb of 7680px for files larger of 7680px. I assume also thumbs of 5120px are never created for files signifcantly larger than 5120px. Thumbs of 4320px will be created only in very few cases. and even thumbs of 3840px will more often than not fail, if the image is much larger than 3840px.

What should have happened instead?:

A solution would be to never create large thumbs but to deliver a thumb of 3840px for all requested thumbs of more than 3840px - or better: tweak MW, so that larger thumbs will be created.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

The media viewer uses thumbs of 2160p height, meaning that the media viewer will often fail to show a panorama image (for example a 20000x2200 panorama).