I am able to edit the stage.js file to display larger thumbnails, however, the resolution of the thumbnail is poor, so I just get a larger blurry image. I've tried editing the plugin python files, but that doesn't seem to make a difference. The thumbnails are still created in the low resolution.
Can an option be added to the powerpoint and image plugins to set the thumbnail resolution? I assume too large of a resolution would cause lagging in the stage view. However, an incremental increase would at least make the thumbnails usable.