No secret, when I stumble over an old gallery I think there must be more from that girl or this time period on this site and I try the usual things, playing around with numbers in url, searching on google or yahoo (is often better) with parts of the url. This way I stumble over many other cute girls from that time period and I collect the links.
Unfortunately, in the case of Nastja, I did never come up with more than the pics above.