Did the page load correctly or did it timeout? Did the program say the images were being downloaded?
Perhaps if you farmed out the functionality to a method, then you could call it just for page 450. Something like:
for i in range(0, 526, 15):
save_images(url % i)
And then if you wanted to check a particular page:
I tested it on 450, and it seems to work fine. Perhaps the page is timing out, or maybe it doesn't like you requesting so many pages so quickly. Perhaps put in a "time.sleep" function at the end of the loop to ensure that it waits a few seconds before the next page.