What program did you use to create said backup image?
As for keeping images...that's up to the user. I keep all of my images (made with Macrium Reflect) because I have much more storage than I need and I have no real reason for removing any of them. I doubt if I will ever need any beyond the most recent...and probably won't need that (I don't mind doing clean installs and I retain installer capability for any programs that I may have use for). But I don't recommend that approach for anyone .
The main thing that I suggest for backing up...is that the user wants to feel that he/she has access to needed/wanted files...when things go wrong (as they do each day). If those files are included in the most recent backup performed...there is no reason to keep backups made prior to that date.
Of course...it's wise to ensure that the recorded/stored backup actually works as it should, before deleting anything.