One of my favorite things about XenForo is the ease of posting pictures...
I'm not sure it will work as easily on an Apple, But using Chrome on a Windows box, it's as easy as opening an image in any application, using the system clipboard to 'copy'. then clicking in your message and pasting. I just tested it in off topic to make sure it works on NovaJeepers, and it does...
On windows, open an image in photo viewer, right click the image and select "copy", Then right click in the post editing window and click "paste". No need to use the "Insert Image" dialog.