So...I removed my Sims3 folder to force it to build a new folder because I was having issues....my dcback up folder is now full of items...and I haven't installed any custom content with the installer because my installer has never worked, it always crashes...
Using dashboard the files are not duplicates or conflicts with any of my other .packages
Using s3pe to examine the files, these are all my downtown lots, city hall, Doo Peas Corporate Towers, a chamber door (?), Fancy Pillar Box....
So I wouldn't just go and delete them...use dashboard to make sure they are not duplicates.