from https://github.com/mattermost/platform/issues/1981, Currently you have to click a button in order to select and image, and it has to be a rectangular image already. Instead, it makes sense to do things more like twitter or flickr, where you can either click-to-browse or just drag-and-drop an image onto the UI, and then the UI gives you the option to crop and scale, so you can pick any image and then just select the rectangular subsection you want to have act as your profile picture.