I have made a tool that allows you to copy the custom maps that you have downloaded to the custom map folder. I have attached the file or click on this link to download it-http://www.mediafire.com/?vxvm2mxzi9gktg4
Sorry but this tools only works with Windows 7 and Windows Vista.
I am working on the tool for Windows XP.
I am also sorry but you have to download the maps in C:\Users\USER_NAME\Downloads.
1. Download map you want.
2. Run the tool.
3. Open up Creeper World and click Custom Maps.
4. PLAY THE MAP AND HAVE FUN!Thanks Echo51 for the help