Giant Cluster Bends, Breaks ImagesExplanation: What are those strange blue objects? Many of the brightest blue images are of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant cluster of galaxies. Cluster galaxies here typically appear yellow and -- together with the cluster's dark matter -- act as a gravitational lens. A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light. The distinctive shape of this background galaxy -- which is probably just forming -- has allowed astronomers to deduce that it has separate images at 4, 10, 11, and 12 o'clock, from the center of the cluster. A blue smudge near the cluster center is likely another image of the same background galaxy. In all, a recent analysis postulated that at least 33 images of 11 separate background galaxies are discernable. This spectacular photo of galaxy cluster CL0024+1654 from the Hubble Space Telescope was taken in November 2004.
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But you are right, the different lensed images have to arrive at the Earth at different times, because the different lensed images follow different paths through space to the Earth. Indeed, if a supernova was to appear in one of these lensed galaxy images, astronomers would wait with bated breaths for the appearance of the same supernova in the other lensed images. It would be a tremendously important observation, leading to a treasure trove of facts and discoveries.
I see Chris has already answered this. 
