I currently use AllDup
The user interface is not very intuitive, but it works well finding duplicate images. It has several image hash function (aHash, bHash, dHash etc), and you can also set the minimum percentage matching of the two pictures.
Don't know what your operating system is but if you use windows then AllDup is great free app that can find duplicate vst files (and also great to find duplicate sample files) in your folders and drives. It has a lot of (file filter) features that can fit your needs and instead of deleting, it can move files to a specific folder so you can review before a permanent delete. When done, rescan under manage plugins:
i use the freeware ALLDUP if file names are consistent across copies use simple filename, if names are messed up i would recommend search method of "file content"