Human Resources probably frowns on these cards but you can probably argue that you were just trying to raise company morale by making the workplace a more cheerful environment. They probably won't buy it though: they never do. It might not be a good idea to send these greeting cards around the office unless you feel like getting fired. We are not experts on differentiating Workplace Inappropriate from Appropriate and we have cards here advocating arson for God-sakes. Maybe you could table this question in a meeting?