Also have a look at CustomizeMii and ThemeMii
ShowMiiWads is a 'Wad File Manager' for Windows.
It displays information about wad files, edits them and give a preview of the Banner and Icon.
New since Version 1.0 is the included NAND Backup Browser 'ShowMiiNand' which displays all titles installed in your NAND Backup (No BootMii Backups!)
Please just link donwloads to http://code.google.com/p/showmiiwads/downloads/list instead of mirroring the archive, thanks!
Due to some people stating this as a piracy tool, I just wanted to clarify that I'm all against piracy and this tool was never intended to be used for!