Although sending risque text messages to a romantic partner can liven up a relationship, doing so outside this context has pitfalls. Anything sent is potentially in cyberspace forever. Should things go sour, the person could easily disseminate steamy texts or pictures to someone else, causing serious embarrassment.
Sending risque text messages or photos is also called "sexting." Sending these kinds of messages unsolicited could be considered harassment. If the sender and receiver have not become comfortable with sexting, it could lead to awkwardness and ruin a budding relationship. Also, in online dating there is no way to know what the person is capable of doing with the texts or images; the images could be leaked onto a pornography site or shared elsewhere on the Internet, where they can spread like wildfire. Having teachers, coworkers or potential employers come across such images could seriously harm a person's reputation.
There's also the issue of sexting people of unverified age. Sending an explicit text message or photo to someone who is not of the age of consent could lead to serious legal trouble. It's always best to verify how old the person is if possible. When in doubt, don't send or request sexually explicit images.