Random textures

Hello! I wank to make a Gallery-game. I'd like to make such thing.. When I'm walking as a First-person Character and look at pictures (just a box for example), I want program to change images on that boxes.. I can put images on boxes but I should make textures from it and then put it on box, but I want to do it automatic. I have different images in .jpg and .png formats and I want unity to chose ithem in random way and put on boxes. How can I do so? I saw somewhere that I can do random-chosing from array, but how can I store pictures in array?

Thanks.