Manual:$wgShowArchiveThumbnails

Thumbnail settings: $wgShowArchiveThumbnails
Whether to show thumbnails for old images on the image description page.
Introduced in version:1.16.0 (r53130)
Removed in version:still in use
Allowed values:(boolean)
Default value:true

Details edit

Whether to show thumbnails for old version of images in the "File history" section of the image description page.

If this setting is false, the "Thumbnail" column of the "File history" table will not be shown. However, thumbnails of old revisions can still be viewed by manually entering an appropriate URL.