Downloads multiple pages

And added size label (quality) as a command-line option.
Not really. The exception thrown when the photoset doesn't exist and when you ask for a page that doesn't exist (i.e. the break condition) is the same. And you want to throw the exception if the photoset doesn't exist.

Maybe there's a way to get the number of pages in advance, but I wouldn't spend too much time on this, TBH.