From what I can piece together from the scant information provided, the image you have chosen for the SHOW BBCode button isn't displaying as you want somehow. First, check to make sure the image is the right size...these button icon images should be 16X16.
You see, when you are asking for help with an issue, it is in your best interest to provide the best information possible describing the issue with which you need help...otherwise the folks who give help have a hard time helping you. If you leave it to others to try to decipher cryptic posts and unclear images, most will simply move on.
Please take the time to actually describe the issue as completely as you can (this may take more than 1 sentence) and please provide a better screenshot so we can actually see what is wrong, based on your description.