I reckon your images have a background colour specified in CSS. That
overrides the transparency the maps images need.
If that's not the case then we'll need a link to do some analysis.
No, you misunderstand me. In your CSS you have something like
img { background-color: #CCCCCC; }
which replaces the transparent parts of images with grey. You need to
countermand that for images in the map, perhaps with something like
#map img { background: transparent }
...but you may need to experiment.
> I will post a link to the page as soon as the site goes on-line.
Which of course will be too late. But better than nothing.