Would
#mw-category-media .thumb { display: none; } in monobook.css do
the trick?
Probably, but she asked for a JS solution, not a CSS one ;) However, it
still doesn't fix the filenames problem; to /properly/ fix it would
require either a server-side change (via preferences) or some sort of
custom rendering pulling the raw data from query.php via AJAX and then
parsing and displaying it.