You can either:
1) Model a box in a 3D package (shouldn't be too hard!!!), unwrap it, apply your textures and voila. One single box, each face unique.
Or
2) Create a box shape by creating 6 plains, rotated and positioned correctly (around a central point.. perhaps make them limbs of a hidden object), and texture each plain.
Depends if you need to do this during the execution of your program or not as to which choice you make. Personally I'd go for the first option, unless I was mapping something unique onto each face of the cube (which I've done before), in which case option 2 works great.
Bite my shiny metal ass