This is what happens when you don’t correctly clear out a render target before using it — you get random texture data.

The big X is part of a close button used in a not-yet-and-maybe-not-ever used GUI toolkit I wrote a few months back.  Much of the rest of the visible oddnesses are font pages and the textures for grass and clouds.

(And yes, the remnants of old graphical data are actually drawing on the surface of the terrain.  If you look closely, you can see the broken textures actually bend to match the terrain shape as they pass over mountain ranges and other terrain features)