That message is from the 'Suicided' damage type. I'm not quite sure whose portrait you would want to display (the killer, victim etc.) but you might be able to handle this by adding some classes via a mutator.
class GameInfo tells the BroadcastHandler to broadcast the kill messages. BroadcastHandler takes that info and passes it to the pertinent playercontroller via the ReceiveLocalizedMessage function. This function then may post the message to the player's console, but also sends the message received notification to the player's HUD via calling 'Message.static.ClientReceive'. It is then up to the HUD to draw the message.
You can then browse through the HudBase and HUDCDeathMatch classes to see how portraits are drawn for when other players/bots are talking. You would need to do something like that for death messages.
Without replacing the HUD, there may not be a real way to do this cleanly. You could use a custom HUDoverlay, or perhaps better a custom interaction (since they appear to receive messages directly) to do the drawing of the portrait.
