Excerpt from their website:
The Mii Mega-Mall is an integrated approach to Mii sharing. What does that mean? It means that, now, instead of having to use many separate processes to get those adorable Mii off the Internet; you can use a single, streamlined approach through this one tool.
The Mii Mega Mall provides a single access-point, with a unified, consistent interface for sharing and retrieving Mii over the Internet. Everything that you need is included. It features
# Built-in RSS capabilities
# Download Mii from the Mega-Mall
# Multiple simultaneous downloads
# Transfer downloaded Mii to your wiimote (using Bluetooth)
# Copy Mii from your wiimote to your PC (using Bluetooth)
# Upload your own Mii to the Mii Mega-Mall to share with others
Anyway it sounded cool, I haven't tried it yet but seems like a easy way to get celebrity Mii's from the net.