Poor quality graphics on export for LMS

Hi there....

Just wondering if anyone can shed any light on how to optimize quality of graphics in exported Storyline courses for LMS.

Here is what is happening:

I Photoshop the buttons and graphics and export to transparent PNG, and import them in to Storyline for use.  When I export the course and view the HTML5 version, the graphics are exactly as I intended them.  However, when I view the default output file (which obviously invokes the Flash version) the graphic quality is appalling (blurry, mosquitoes, etc). I have even set the image quality settings in the Publishing window to 100% and it makes no difference.

So...

What are the best methods in creating buttons and graphics for SL and preserving the quality in Flash?  Should they be saved in high quality TIFF and then imported?

Apart from this issue, I am absolutely loving Storyline!