Feature summary
try https://commons.wikimedia.org/wiki/Special:Search or https://commons.wikimedia.org/wiki/Special:MediaSearch , both have the same problem.
try searching " typewriter " or " nurse ", etc.
for Special:Search , untick file namespace and/or gallery.
for MediaSearch , click "Categories and Pages".
you will have a hard time finding Category:Typewriters or Category:Nurses . lots more other cats appear before these.
Solution
whatever the keyword is, " Category:<plural form> " is usually where files about that keyword are categorised. the plural form is often the -s form.
i guess "search results sorted by relevance" are sorted by some kind of weight? increase its weight if " Category:<search keyword>+s " exists and make it appear as top as possible.
Benefits
users want to go to the category. give them that. dont waste users' time.