The functions that SDPhantom mentioned aren't functions you use, they are what transform the special {} strings into icons in clients that receive your message.
All you need to send a raid icon in chat is a certain string, no functions or anything special. Copy any of these and use them directly in your chat with nothing else to test them out:
Code:
{rt1}
{star}
{gold}
{rt2}
{circle}
{orange}
{rt3}
{diamond}
{purple}
{rt4}
{triangle}
{green}
{rt5}
{moon}
{silver}
{rt6}
{square}
{blue}
{rt7}
{cross}
{x}
{red}
{rt8}
{skull}
{white}
The following function call will send Hello World surrounded by skulls into the general channel:
Lua Code:
SendChatMessage("{rt8} Hello {skull} World {white}", "CHANNEL", nil, 1)