Chart Axis Background


What is the best way to get the frame of the chart X and Y axis?  I want to style each with an image background.  


I just found the axisFrame property, but what is the best way to style the axis with a gradient or image background?  Do I really have to get the axis frame and position an view behind the chart and update it’s frame everytime the chart redraws?


So, even if I get the axis frames, they are always the same as the chart bounds.  Is there really no way to style the axis background?