There should be a PANORAMA (or LANDSCAPE, whatever) magic word specifying that a category contains very wide images. This would then allow MediaWiki to optimize display. Instead of say 6 images per line with thumbnail dimensions "120 x 35", it would have one thumbnail per line, perhaps "800 x 235".
It might be better to allow specifying the exact thumbnail size for a given cat, but that's not at all necessary.
Version: unspecified
Severity: enhancement