Various (command line) ways to find the format of an image:
identify FILENAME(requires imagemagick)
sips -g all FILENAME(OSX only?)
Getting better images from various sites:
170x170 (or sometimes
100x100) in the image URL with
1200x1200. Be wary of upscaled images if using the 1200x1200 versions.
._SS400_.jpg at the end of the URL with just
.jpg (sometimes the letters and numbers are slightly different but it always starts with a dot and an underscore). This will usually get rid of any white borders around the image too.
Click the image to go to the page with the full images. Even when there isn't a "more images" link, the page will often have a larger front image.
1.200.jpg, etc., at the end of the URL with
cover_160.jpg, etc., at the end of the URL with
serve/500, etc., with
t500x500.jpg (or whatever) with
original.jpg at the end of the URL (you can just remove the question mark after
.jpg and anything after it)
You need to register/log in to access high resolution images.