You can follow the steps mentioned below to transfer/copy any data received through apps like Instagram, Viber, Kik, BBM whatsapp .etc. to your PC.
Here Whatsapp is used as example.
1) Through Android Tab Launch the ES File Explorer. (Refer here to know how to install ES file Explorer).
2) Click / Tap on the WhatsApp folder.
3) Click on the Media folder.
4) Click/Tap the folder from which you want to copy the files
5) Select the images to be copied by long pressing them and select copy to option from the bottom right.
6) Select the Windows -> BST shared Folder to copy your files.
7) BST shared folder on Bluestacks 2 is mapped to windows, and can be accessed at the following location on your PC
C:\ProgramData\BlueStacks\UserData\ShareFfolder (This location depends on the installation path you selected at the time of Bluestacks 2 installation)
9) On your PC, open the above location to get the files.