Although rules of etiquette and "netiquette" are much more relaxed in current times than in years past, it's still a good idea to limit cards with off-color or devilish humor to people you know very well.
Halloween Express: Here, you'll find quite the miscellaneous corset collection, from devilish styles to those that look as innocent as a modern corset possibly can.
The following sites either specialize in devilish humor in their e-cards, or have good collections of cards with off-color and naughty humor.
He laughed, his eyes sparkling with a devilish thought.
As no one could curse Jesus except under the influence of a devilish afflatus, so none could say "Jesus is Lord" except he was inspired by the Holy Spirit.