that is one easy task...
first you need to have the following.
1.download es file explorer or any other file manager of your choice
then install the application in bluestacks.
after that you need to locate the folder called windows in your bluestacks sdcard and find another folder called BstSharedFolder.
this is the folder that connects directly to windows hdd.
you can find the location of the folder in
now lets solve the tasks.
if you want to transfer images from bluestacks whatsapp to your pc,
just move the folder in the location in your bluestacks sdcard/windows/bstsharedfolder
then they will be available in your pc directly.
and if you want to move them from your pc to your bluestacks sdcard,
copy them to the directory,
then from there just open bluestacks navigate to your sdcard/windows/bstsharedfolder
then do whatever you want...
I hope this helps...