I also collect valentines. Well, I have a few dozen, nothing more. I have to draw the line somewhere. I still love looking at them. Wonderful illustrations meant to bring some sort of gut reaction. Usually they just make me smile.
There's a wonderful book put out by Taschen entitled Valentines: Vintage Holiday Graphics which is nothing more than page after page of valentines. It really runs the gamut from romantic to pure silly. No information is given about any of the illustrators. I fear that information is long since gone. But I do find work in the book that is similar to some in my collection. I can imagine people searching and searching for one particular illustrator. Good luck with that.
I've posted a link in the left column to the book at Amazon where you can read more about it. Don't be alarmed that it says French and German edition. This simply refers to the preface which is provided in English, French, and German. There's no text in the rest of the book. And the trim size is very nice. Makes a nice reference book or a wonderful gift for someone who loves valentines.