...and i just wondered is it possible to have a custom firmware not just a theme but a whole new interface...
This part makes me wonder...do you even know what firmware really is?
Firmware is basically the code that connects the software to the hardware. It maintains the various input-output tasks. Tasks like remaking the interface have nothing to do with it: that's on the software level. Take your PC: the firmware is what's in the BIOS. You can upgrade or change it, but it won't change anything on your hard disk.
Now...the wii is a bit of a special case because it doesn't use "one" firmware that contains all the code, but many firmware's (called IOS'es). The wii is built so multiple of those IOS'es can be loaded. So if a game developer wants to use a different peripheral (e.g. the balance board), he just writes another IOS than another game. It also makes things easier for hackers: rather than replacing perfectly fine IOS'es, they just write new ones that are put right next to the normal ones. That's what fenrinwolf means when he says there's no need to replace those things.
And as for changing the interface...in a way: yes. Priiloader allows you to change your booting sequence from the wii menu into a homebrew program such as configurable usb loader. Thanks to forwarder iso's, configurable usb loader can display pretty much all channels from the wii menu.
So basically: when I start my wii, instead of the wii menu, I see configurable usb loader's screen with all the applets that I like and use. And all with barely touching any firmware whatsoever (the wii menu is still on my wii...somewhere).
QUOTE('mew512')So i would put my nand on an sd card and then sneek runs that?