This is the third functionality enhancement I've implemented so far. First came the quick reply mode overhaul. Then, the spoiler button (both things changed the same day). It was time to "solve" the lack of image hosting in ProBoards.
Instead of having to go, to all the trouble of uploading the image to an external hosting site, we now have the option to click on the new "Add image to post" button. A new window will pop up, or you'll be directed to a new tab (depends on the browser).
Simply browse for the image in your computer and upload. The window/tab will close and you'll be back in your post, with the image already inserted.
I forgot to include pictures of the actual button. You can only see them if you're logged in. Yes, I said "them", because there's two, one for quick reply mode: