you would have to figure out how a site such as www.garfield.com names the newer comics. there are many sites around the Internet that carry comics (yahoo.com, kingfeatures.com, etc.). So the only key is figuring out how they name the comic (gar10-14-02.jpg, etc.) and using the code to reflect that.
www.ucomics.com is a nice site for leeching...erm, getting comics from, they're usually in the format
ucomics.com / comics / ga (comic name) / 2002 (year) / ga021015.gif (comic name | year | month | day )
which will get you the URL for todays garfield via ucomics, un-fotunately it seems they don't allow external linking of images, if anyone knows of a site that does then that code could be adjusted for it....