Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
It's from Smogon's CAP type bars, which are located at http://cap.smogon.com/web/media/types/dark_big.png, replacing "dark" with whatever type you want. You know, if you want to know the URL of an image, you can just right click it and select the "Open Image" or "Copy Image URL" option of the dropdown box, so you don't have to ask these kinds of questions. :D