When Lisa Harper of Stockholm saw her two-year-old son, Ethan, snuggling with "Harp," the family's pet golden retriever, she knew it was a picture she had to take. And when she heard that PicturesMatter.com was running a photo contest called "Pets are Family Members, Too," she entered her picture. Last week, after learning she had won the national grand prize of $250 plus an $800 package that included a digital camera and a professional portrait of her family, she went to Sharp Images in Stockholm, where Steve Lasher, director of PicturesMatter, presented her and Ethan, now 3, with their prizes.