Why not rename the files from within FTM? If you have done your census workup for your families, you will have many census images in that folder.
If not...
1. Rename your FTM2009 file and media folder from xxx.ftm and "xxxmedia" to xxx2009.ftm and "xxx2009media"
2) Open the file in FTM2009 (xxx2009.ftm) and go to File > Export, uncheck "include media" and change the file name to be xxx2009nomedia.ftm. Save in that folder.
3) Create new folder with name something like: "FTM Files 2012". Copy xxx2009nomedia.ftm to this folder and rename it xxx2012.ftm.
4) Make your normal daily backup (to your external drive or carbonite or whererever.)
5) Open FTM2012 and go to file > open. Navigate by browsing to your FTM Files 2012 folder and click on xxx2012.ftm.
6) Begin adding & renaming media files through the person page for each person - or the source workspace for each citation. Be sure to say you are ATTACH TO (ie adding) the media file for the first time it is used. Then, LINK that file to each person or citation after the first one.