I've found the mother lode.... of vintage Valentine's that is. While browsing on Flickr I came across the photostream of James Kimberlin
I'm just posting three of the images, there are 58 in the collection . The images are great quality, high resolution, and some of the cheeriest Valentine's I have seen. You had to know this puppy one below would be my favorite.
For those of you who love to make paper crafts or other creations from vintage images, this is a great library of artwork. You can see all of them (and the usage rights) over on James' flickr page , (his profile name on Flickr is Valart2008) by clicking here.