I am trying to decrease my widget Icon which appears on the header, I tried but not getting any idea ,can any one please suggest me how can i do it.
To make the icon look smaller, you can create an image with more transparent space around it. Depending on your image program it might be called something like "Resize canvas" or "Image->Canvas size..." (the latter in http://pixlr.com/editor/).
While Robert's solution works, the above following suggestion doesn't require any code changes, only some image manipulation 🙂