hiya mike,
The image you use makes a difference as to whether or not it will fill the screen as is or if it will repeat like it's doing. If the image isn't big enough to fully cover the area, what happens then is it either cuts off where the picture ends, or it repeats itself depending on if you told it to repeat or not.
In the case of your graphic, it's not large enough to fully cover the area and instead it just starts to repeat. You can resize it to fit better if you're able to do so using a graphics program. You'll of course want to be sure it's sized correctly for a wide screen view so that it doesn't look distorted and such.
