Event lists all show a calendar marker of 31?
Using Jamroom
It depends on where it lives at.
If you're uploading a new image to a version of a jamroom skin say
/skins/jrElastic-version-1.1.2/img/SOME-IMAGE.jpg
and then jrElastic-version-1.1.3 comes out, it will be found at
/skins/jrElastic-version-1.1.3/img/SOME-IMAGE.jpg
The old image will still exist at the 1.1.2 location, but the new skin will use its version so it would revert.
However if you're thinking about a location like
/data/media/0/0/?????.jpg
Then those files have been uploaded to the system and would stay there as long as they are not re-uploaded over.
But a location like
/data/cache/ (anywhere)
would only last until the cache was cleared.