I made a thingumabob
I wrote a small python script to allow the validation of single IIIF manifests, or a folder of manifests. It can be run via the command line, or imported as a module into another Python application.
The code, and full usage instructions can be found in the GitHub repository.
The script utilises the IIIF manifest loader and factory scripts from the IIIF Presentation Implementations repository, so much credit to Rob Sanderson at Stanford for those.