On click, attached images start downloading. This is very uncomfortable (click starts download > (save somewhere) > find back > open > see, that is 3 or 4 click). Instead, everything viewable from within a browser (images, pdf for most browsers, audios and videos) should open in a modal pop-up (click > see, 1 click).
Other (other than media) files should directly open. Download should be a secondary option.