well.. you can try something like this..
after you have positioned your chart and sized it properly to fit the page..
take a screenshot of the page..
paste the image into photoshop or ms paint...
and cut the chart alone and create a sperate image..
make that image white... and then overlay your logo and position it at the bottom right corner..
and save that image..
now use this image in your chart background..
hope that helps...