We use Cells to create charts for PowerPoint presentations and use the ToImage() method to display a picture of the chart until it is activated. Problem is that although the chat area is set to transparent the generated image has a white chart area which doesn't look great if the slide has a color background. Any chance that the image can honor a transparent chart area?
Addendum to my above comment - it does work for PNG image format. I usually use the EMF as that scales nicely for various chart sizes. Do you know if EMF supports transparency?