The upright parameter should be added to images whose height is larger than their width. It is a best practice documented at Mediawikiwiki and at some other wikis:
- CS: https://cs.wikipedia.org/wiki/N%C3%A1pov%C4%9Bda:Obr%C3%A1zky#P%C5%99%C3%ADklad (see the “upright” bullet point)
- AR: "معدول" https://ar.wikipedia.org/wiki/%D9%85%D8%B3%D8%A7%D8%B9%D8%AF%D8%A9:%D8%B5%D9%88%D8%B1#%D8%B5%D9%88%D8%B1_%D9%85%D8%B9%D8%AF%D9%88%D9%84%D8%A9
- FR: https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Mise_en_forme_des_images#Cas_particuliers_:_vignette_associ%C3%A9_%C3%A0_upright ("Vignettes verticales")
How an article looks like with upright and without it.