It would be great if reviewers were allowed to upload files of their own. An example would be: I start a review request and attach a Word document for review. The reviewers take it, add their comments (within Word), then attach their version of the document. In this case Review Board wouldn't really be used for any diffing, just a place to collect all comments, etc before moving forward. Discussed here: http://groups.google.com/group/reviewboard/browse_thread/thread/df9f2082640399e8
I'd like this too - when reviewing code for web applications, it's useful to not only be able to review the code and leave comments on that, but upload screenshots with comments showing where the page isn't rendering correctly, etc. It's not possible to leave an "image comment", so the workaround we've been using is giving reviewers admin rights, which allows them to attach an image to the review, but also opens the door for them to do anything and everything. Ideally, it should be possible to let reviewers add images (with comments) without making them admins.
I've found it's possible to let reviewers add images, with comments, by giving them this user permission: reviews | review request | Can edit review request This is a lot better than making them super-users! However, it's still possibly too much power - they can not only add their own file attachments, comments, etc., but they can also edit the review and upload new diffs.
I would think that your editor should be improved in such a way that reviewers and reviewees are enabled to just paste screenshots into the editor window alongside text they are writing. Maybe you even want a image editor that allows markups. I am sure there is some open source editor out there that provides this functionality. Thanks. I really like reviewboard.