It would be very nifty if the plugin supported the possibility to use auto generated thumbnails of image files and perhaps also pdf's. I see that you use google docs to preview files, and I can also see that google doc/drive generates thumbnails of a lot of file types. I don't know if this is available for you to use too though, but it's an idea.
Several people has asked for this feature, and I sincerely hope it will be implemented in the near future. I do understand that you have a lot of other features on your plate too though, but it's certainly on the top of my list of wishes