Something I would find very useful would be:
1. The ability to 'Replace' images once they are place on a board. If I am uploading a bunch of designs/wireframes, often I am updating them outside of RTB based on client feedback. I then have to upload them again. It would be really helpful if I could just go back to the board, click on an image and 'replace' it with another image from my computer - which will be resized to the same width.
2. Something that bugs me is if I upload a folder of images, they seem to get all jumbled up. I had a series of 20+ JPGs that I wanted to upload and then place on the board in order (it was a walk-through of a website). They were number 1/2/3 etc in my folder in Finder. But when I upload them, they get all jumbled up. So I have to manually reorder them on the board, which is a real pain. This would be a great improvement in my eyes!