@hardner,
I am not exactly sure how you are adding your background image. I have done wafer maps using a shape file.
Also, the script below from the Scripting Index > Display Boxes > Add Image provides an example using boundaries.
I would probably create a Add-in or hot key script that prompt you or the user for the product and/or sampling plan then via JSL select the image, set the scale and the boundary. If you have multiple graphs (By group or multiple Y or X), the script could get the current window find all FrameBox and set it at once.
Providing a few more details, would likely generate more suggestions/help.
Names Default To Here( 1 );
img = Open( "$SAMPLE_IMAGES/windmap.png", "png" );
w = New Window( "View Image",
Graph Box(
FrameSize( 500, 500 ),
X Scale( 0, 100 ),
Y Scale( 0, 100 ),
<<Add Image(
image( img ),
bounds( top( 90 ), Left( 10 ), bottom( 10 ), Right( 90 ) )
)
)
);