ScreenshotUploader allows you to upload images to Imgur or Lutim (can be set in the config) by holding U when taking a screenshot. You will then be provided with an upload link, as well as a deletion link.
The mod also prevents the game from freezing when taking a screenshot.
You may have to select Imgur in the config, as Lutim has been shut down.
The mod contains the Apache HttpClient MIME library, which aids in uploading the images. It is licensed under the Apache 2 license.