Hey hey, welcome to our wonderful PokeMMO community!
I hope you'll enjoy this game. ^_^
If you need anything about the game or the PokeMMO forums I'm here for you.
The Soul Silver rom is just to see your Pokemon behind you.
You won't have a new "design" with the Pokemon Soul Silver rom or the Pokemon Heart Gold rom.
But if you want a new "design" of PokeMMO, you can use some themes and mods in "Client Customization".