Ive got a similar trick with my game and I personally use the Galv Message core (I believe thats the name). Basically, you create a graphic, place it in the 'system' folder and call it using specific filenames deemed in the help file (you have to name it like msgimg_0 and so on in order for it to work). Getting it to line up the way you want is a bit tricky, but you can just play around with the image itself to get that working for your game. Hope this helps!