If your background is not white, you'll have to change #FFF. (#333 is the color for the Grunny Theme)
#profile
{
background: #FFF url('NEW_AVATAR') no-repeat 1px 65px;
}
#profile .avatar
{
filter:alpha(opacity=0)
opacity:0;
}
{
background: #FFF url('NEW_AVATAR') no-repeat 1px 65px;
}
#profile .avatar
{
filter:alpha(opacity=0)
opacity:0;
}