To set the position you need to chose the repeat valueand where on the X and Y axis you want it to land.
Backgrounds can be fixed, scroll, and local. Fixed keeps the image in the same position while scrolling a page. Scroll allows it to move with the page. Local makes the image scroll with the contents of an element.
You can change the size of a background image by setting a percentage, or setting the height and width of the image. To set the size in pixels, you set the width and then height.
To position a background image using edge offset values, you must first set the relative position (right,bottom) and then the number of pixels from the edge (background-position: right 5px bottom 10px)
The color of a background must be set last in a multiple stack background or it will cover all lower images.
The background element has many different properties that must be set to get your background in the position and layout that you desire.