You should think carefully where the bottleneck is. You seem to be retrieving several images from the same server. In this case, chances are good that it won't be any more effective if you have several downloads in parallel (unless, for instance, the server has many CPUs and creating an image costs much CPU load). One pipe-lined connection (using HTTP's Keep-Alive) might be more efficient and less aggressive.

I agree with blazar that fork is spelled in lowercase letters.