Displaying a message/text similar to a raid warning.

How would I go about displaying a message also possibly including a image with it on the player's screen?

Something similar to what a raid warning, DBM or scrolling combat text does.|||The easiest way to post text like this is:

/run UIErrorsFrame:AddMessage("This is a really important message!", 1.0, 1.0, 0.0, 1.0, 2);

/run PlaySoundFile("Sound\\Music\\ZoneMusic\\DMF_L70ETC01.mp3") ;

Check out http://www.wowwiki.com/API_MessageFrame_AddMessage for info on how this works. Second line plays a sound.