u added it to the camera which for me in the past has caused some problems
i would do it by creating a poly plane and using hypershade and a lambert
for colour click the checkered box then chose file and rotate so it is the right way up
next use photoshop or a pic editing program to find dimension of pic in cm if that is what ur set up is in(this can be found under preference and i cant remeber the tab but there should be one for units ie pixels metres inch cm and make sure that it is the same unit to wat u found out the size of the pic is in)
add to layer and set as reference
ask again if i was to vague