EDIT: Very interesting. I have found that when I upload the mission and run it in a custom arena, the briefing works as I intended. It just doesn't work offline. After I download the built mission from the server it does work offline.
Just something to keep in mind when making a mission and testing it. You may actually have to upload it to see it working correctly.
I did not expect that.
I have tried to upload an image to show on the screen when the curtain opens in the briefing room, but have had no success.
I've tried both jpeg and bitmap, I've tried them in 128, 512, 1024. I've tried to set the event for the same time as the curtain event, I've tried to set it for a later time, I've tried to set it for an earlier time. I've tried placing the image file in the misres folder, I've tried placing the file in the mistemp folder.
I have pretty much run out of things to try.
Anyone have any ideas?