on the map buriel mounds, there is a GIANT smiley smack- dab in the middle of the map...actually theres 2:

1. When you are trying to leave the map by climbing up the rockslide, get to the top and look straight out at the other side of the map, you should see a white shade in the rock wall, look to the left, another dot. now look for the crescent-shaped burn marks on the ground, and under those 2, a SMILEY!

2. When you do manage to leave the level, head toward the "enterprise" ship. Then run into the large open area next to the CTF base, there are burns on the ground. if you look carefully its another giant smiley!