How to make user profile image reflect a transparent background?
If the image background is transparent when you hover over it, then the picture has transparency, and must be a .png or .gif file.

Therefore the white background must be down to CSS

In Chrome or Firefox, right click on the image and select "Inspect Element". Find the CSS controlling the div or img, and change the CSS from

.picture {
   background:#FFFFFF;
}


to

.picture {
   background:none;
}