New Photo Type not showing thumbnails

I've created a new class that inherits from the GalleryPhotoItem class and has minimal overrides. I can upload them correctly and they show up in my new table, but I can't get them to generate the thumbnail. On upload it runs the "Create Thumbnail" option. Is there something deep in the code that I need to register my class for? The files I'm uploading are simple jpg files. I can "Upload them from browser" and it will created the thumbnail correctly. If I upload them through my ItemAddOption it doesn't seem to create the derivatives.

Thanks,

Jon