Currently MultimediaViewer may display not very relevant images like icons.
It is possible to ignore them by using <span class=metadata> (is that documented somewhere by the way?), but unrelevant files may not have been tagged yet with it.
A user on fr.wp suggested that MMV should simply ignore any file that is used in articles at very small size.
Version: unspecified
Severity: normal
That seems very unintuitive. Would you skip e.g. the image at https://en.wikipedia.org/wiki/Graphics_Interchange_Format#Uncompressed_GIF ?
Mass-removing the Multimedia tag from MediaViewer tasks, as this is now being worked on by the Reading department, not Editing's Multimedia team.
If you mean the placeholder image shown while the full (screen-sized) image is being loaded, the logic for that is here; you can modify MAX_BLOWUP_FACTOR / BLUR_BLOWUP_FACTOR_THRESHOLD locally, or write a patch for providing a hook in which it can be done.
If you mean that the image should be displayed in a larger size than the available screen area, see T77151: Full Zoom Feature in Media Viewer (probably quite hard to do well).