Originally Posted by Verdasco
Or is it just from a website where all the photos are big?
yes, in most cases I would say, it is like that.
In less cases, sometimes a link to a picture can be bigger than the image appears on a page, but it's not often. For example, the real size of a picture is 600x400, but in the coding of the homepage you can say that it only takes the dimension of 300x200.
And in general, you can always make a picture bigger, but not without loss of quality. But that's not what you're meaning here