I have been recording image numbers on all my entries for the past year when I started my genealogy research. I have found it extremely useful whenever I needed to go back to locate and review a record. Downloading and or printing all these records just seems like an arduous task. There have been many times that I have found a record that was not in correct chronological order. Sometimes the parish records alternate dates between the main church and an auxiliary location. And of course sometimes the date recorded is inaccurate (for example Jan 2013 is recorded as Jan 2012).
Well in fact the Jalisco parish records I research were updated on Feb 25. To my surprise I noticed that my entries for marriages for Juchitlan 1860-1878 records no longer point to the correct image! Upon further inspection I discovered that they added about 50-80 images to this particular collection, which makes absolutely no sense since the new images added were for marriages from 1922. I do not yet know if

David

I would not go so far as to say this is a bad idea, but you need to know the issues with such a citation.

The FHL is simply a repository of a copy of these records. The film number, image number are simply from their system of cataloging and presenting the record. The url of the source is simply the current electronic repository, which (1) may change as systems are updated or (2) could simply go away if the system becomes unfunded or unsupported (for the FHL this is highly unlikely).

I think the proper citation for the record (for church or civil records) should be:
author (Catholic Church or Civil Authorities)
Parish (for church only) and location
record type (baptisms, marriages, etc)
volume number or year(s) covered
page or folio number (if used)
record number if used

Along with this information, you should note the repository (FHL), their film and image number, as well as the date you extracted the information.

Family Search does provide some guidance on citing records