Asynchronously downloading a file

[Deniz Dogan]

I'm currently using find-file to view images fetched over HTTP.
However, sometimes the server hosting the image is kind of slow and
thus Emacs just hangs waiting for the image to fully download before I
can view it.

Is there any existing Emacs functionality which asynchronously gets a
file from any of the protocols that e.g. find-file (tramp?) supports
which lets me provide a callback function?

Thanks,
Deniz Dogan