I rename the media files for ease of sorting and indentification. For census records the format is something like:
It varies a little since the conventions changed for the census over the years, i.e. there was not always Enumeration District numbers for example.
Since I might have several households all on the same census page this means that they can all point to the one media file instead of several -- which can happen if you download the data from Ancestry over many different years or if you got the image from another source.
Makes it easier for me to go and look at an image outside of the program as well since I do not need FTM open to interpret a string of random numbers in order to figure out what media file is associated with what census record.