Just last week I added up my sales for some "cute puppy pix". Maybe 5 pix in series, not exactly a popular series in itself - but what I was very surprised to discover is that I sold more cute puppy photos from the series on BIGSTOCK than any other site. Maybe it's the site to sent that pet photo that you love so much but wouldn't think of submitting.
(http://www.bigstockphoto.com/thumbs/3/8/1/medium/1832384.jpg) (http://www.bigstockphoto.com/thumbs/3/8/1/medium/1832356.jpg)