I wrote a blog post a while ago where I manipulate the thumbnail urls. It might be of use to you: http://world.episerver.com/blogs/Per-Magne-Skuseth/Dates/2015/9/thumbnails-for-blocks/
I used your ThumbnailModelTransform and added my own logic. Thx a lot!
No problem. Glad you found it useful
Is there a way to either:
1. Control the URL that is rendered for the thumbnail
2. Skip custom logic in CreatedVirtualPath event for the thumbnail, but apply it for other images in edit mode (since Name of the sender is the same and I can't catch anything that is different between thumbnail and other images rendering)