My guess is, you're dragging the image from the Google images page, and so using the thumbnail instead of the full size image.
To test this out, I did the search for "i am legend" in Google images, like this:
http://images.google.com/images?hl=en...
I liked the one from wrathofnino.wordpress.com (972x1440, 198k), and dragged it directly to DL2 – but this will only copy that tiny thumbnail image, resulting in what you posted.
Instead, what you want to do it is click the image you like, and then click on "See full size image" from the subsequent page. This opens only the image, and if you drag that, you'll have high-resolution artwork for DL2.