Unlock 6 Unique Graphic Modes
On the main menu enter the "Extras" => "Cheats" => "Enter a Code" and enter "GFXMODES". Then, you should be able to unlock new graphic modes with [L3] button.
Unlock Secret Special Props in Constructor Mode
On the main menu enter the "Extras" => "Cheats" => "Enter a Code" and enter "COOLPROP".