The old gnome-screenshot was a very useful app. Unfortunately it seems to have been dropped in the latest gnome shell. I found this extension that does a similar job though. It’s called Area Screenshot and you can find the code via github
Looking at the Advanced Usage note it seems that the developer added a hook that allows users to run a program after the screenshot has been taken. I used that to upload screenshots automatically to imgur.com. You will need to download the Bash Script Uploader and save it somewhere accessible as an executable. Then create the following script in ~/bin/area-screenshot-post
#!/bin/bash url=`imgur "$1"` notify-send --hint=int:transient:1 "Screenshot Uploaded" "Copied URL to clipboard:\n$url"
You will get the url in the notification area.