Somebody created a image # 2001-2500 add on to that pack but I can't find it now or I'd provide the linky. Good advice above though on using another pack for the #2001+ images, there are many great batch file naming programs that will rename any group of images to whatever you want, Flash Renamer is good (
http://www.tucows.com/preview/209455.html) and I have an older version of the image viewer ACDSee that does the same thing.