I think the gif issue is this line https://github.com/Spuds/Elk_Image_Cache_v10/blob/master/subs/ImageCache.class.php#L243
if( pathinfo($this->data, PATHINFO_EXTENSION) === 'gif' )
{
$extension = 1;
}
elseif ( pathinfo($this->data, PATHINFO_EXTENSION) === 'png' ) {
$extension = 3;
}
else {
$extension = 2;
}
Will probably sort it, I think...