Suppose a person click on the image that said one, and you passed this over (?pic=one)
On your second page you could output something like
print "<img src='".$_GET['pic'].".jpg>\n";
or something like that. It really depends on how the variable links to the picture, and what else you want to output with it. I appreciate what you're asking is simple enough, but you've provided little information so all I can give you is a general rule, rather than one specific for your needs.