you could use ./ instead to reference the current dir, that way you don't have to keep adding the path name, but then you run into problems with sub directories...
should return the path to the current file(eg: /~zluthorg or whatever). but then that doesn't solve your problem completely, since sub dir's will still cause a problem.
my solution has always been to run a single include in all files carrying several usefull peices of info:
then just use it like so:
<img src='<?=im_path;?>my_image.png' />