ImageVerifier (IV for short) traverses a hierarchy of folders looking for image files to verify. It can verify TIFFs, JPEGs. PSDs, DNGs, and non-DNG raws (e.g., NEF, CR2).
IV is designed to process large numbers of images. Folder hierarchies with 100,000 images or more should be no problem. There are two kinds of verification that IV performs: Structure checking and hash checking.