FYI for the new folks: hovering over an image you're about to upload gives you the option to do two really cool things:

◽ Crop - lets you choose where the center of the image thumbnail is (no more unintentional crotch shots on full-body pics!)
◽ Describe for the visually impaired - several mastodon users use screenreaders and describing your images really helps them out! @PleaseCaption is your friend 👍