Hello,
Wikitext editors can have media materials rendered using any arbitrary size (the thumbnails wikitext syntax). Each different size would produce a hit to the server backend which will generate a thumbnail for that size.
The following requests for comment is about having a consistent set of thumbnails sizes that are allowed to be rendered and let the client browser to do the up or down scaling.
https://www.mediawiki.org/wiki/Requests_for_comment/Standardized_thumbnails_...
It would be nice to discuss about it on the list and amend the document with any idea you might have :-]