I just upload to imgbb.com and embed the link here. The best way to help keep Lemmy server costs down is to not upload any images at all. Also, the advantage of using imgbb.com is that you can set your images to auto-delete after a particular period, which also helps keep the costs of imgbb.com down - no point storing your publicly shared images forever, unless it’s something that really deserves to be stored for that long of course.