Using images with various resolutions dynamically

Hi,

I am using images of various pixel resolution .. But when I dynamically apply them using gui texture or merely fixing them on planes they tend to scale to the size of a plane or fixed pixel resolution. I would like to dynamically plant them according to their actual pixel dimensions. If resolutiion does not cover the scene. Then there should be a black border urrounding the empty spaces equally on either side. That may be accomplished though by a black skybox ... But how do I get the images to appear with their intended origins. Resolution .

Thanks, Red.