nginx valid_referers not working

I'm using valid_referers to block access to my website's picture from other site.

I'm using below config:

location ~*^.+\.(jpg|jpeg|gif|png|bmp)$ {
expires 7d;
valid_referers none blocked www.example.com;
if ($invalid_referer) {
return 403;
}
}

It works well in the past.

But now I found that someone just use below method to access my pictures They can access my pictures via URLs like below

http://www.example.com/images/abc.jpg?0.9208715439582744
http://www.example.com/images/0o9.jpg?0.8152212035621078

How can I prevent them to access ?