Possible to symlink a file to a web url?

Maybe a named pipe that you feed with a wget for the file?

Edit - Not wget. You can work with linx -dump. So -

mkfifo reddit
links -dump reddit.com > reddit
cat reddit

There are several nice and interesting solutions here. I especially like @ArjunShankar's fuse solution. In the spirit of keeping it simple though, perhaps a file in /etc/cron.daily with

#!/bin/sh
cd /your/dir && wget -N http://www.host.com/images/image.jpg

would be a lot simpler and Good Enough(TM)?