there is probably an easier way to do this, but here is how i would. Make your glass ( a plane or thin cube) and for your material set your tranparency down to like 10%. For you sticker, make a plane the demensions you want you sticker to be,(make sure the image your wanting has white around the image. Make a new material and for color click the texture arrow and select your stick image. also in alpha do the same. apply that material to the plane. Then all you have to do is position your sticker where you want it on your glass. You can also rescale the plane.