Hello again it just dawned on me that you weren't using css to add the rounded border to your image. The reason you can't fix the problem with the other div colours is because your image is providing its own border and background colour. CSS can't fix that! You would either need to just use images with no border and style the border with css or create png images with the #efefef; background removed and left transparent. The downside to the second option is the files will probably be bigger as transparent pngs.
Edit:
The red portion is just to highlight the border region which would need to be transparent.
Hope that helps