The Scrap Album, a small but exquisite website run by Malcolm Warrington devoted to the history of greeting cards and other paper ephemera, features a collection of not-so-nice Victorian valentines:
"In mid-Victorian England the custom of sending daintily printed valentines, overflowing with hearts, cupids, and poetical posies was generally understood to consist of an exchange of missives between special loving friends. Yet beneath the sweet exterior and tender words of these lace-paper beauties lurked something far more sinister - the comic valentine! These scurrilous printed sheets entered into the humour of the common and middle classes ... fun and mischief were their elements. In reality they were masterpieces of the grotesque, venomous in humour, spiteful and rude, expressing anything but love."
Malcolm's website includes many delightful images of these very unsentimental valentines and equally delightful excerpts from the periodicals of the day.
Related link: "A Flowering of Affection: Victorian Valentine Cards at the Lilly Library" (online exhibition, Indiana University; interactive feature allows you to send a Victorian e-valentine)