This issue is caused by a slow Internet connection or because the Bluestacks application is filtered by the Firewall. I have encountered the same issue, and the fix was very simple: turned off the firewall completely, then disabled and re-enabled the network adapters. Go to Start > Control Panel > Network and Internet > Network Connections. Right click the network adapter you use and select Disable then Enable.
Restart Bluestacks from the system try using right click on the icon and then attempt to download the pictures again.
