The standard cast and crew images are actually embedded into the database files and so unfortunately can't think of an easy way of mass-removing them.
Custom cast and crew shots are stored in a folder called "CreditPhotos". Deleting the contents of that folder should remove all those.

Edit: one way that might remove all the images, though it may not be worth the hassle, is to make a backup of your database, but select custom backup and don't include the cast and crew database or the custom credit photos. Then uninstall Profiler, delete the Profiler folder from your hard drive and re-install the software. Then, when you restore your backup it will use the default actors database with no images in it.