To really make this awesome we need structured data support for Commons with Wikidata. We'll be making more progress on it in the second half of this year but there is a lot to do.
Sure, to really make that awsome, yeah you need wikidata. But we are far away from hitting the point where we need wikidata. In fact the three examples McBride gave don't need wikidata. mime type and file size are easily programmaticly available already. And unless I'm mistaken, functionally dependent metadata like algortihmically determined main image colour, are out of scope of wikidata.
--bawolff