The Half-Life lambda: a white letter inside a ring, sprayed freehand so the edges are ragged and a thin trail of paint runs off the bottom of the circle. The whole picture is greyscale, dark grey inside the ring and black around it. The background is not transparent, so what appears on the wall is a solid black square with the symbol on it, not just the symbol.

A 64x64 wad3, packed at import from the raw 8-bit logo the source page carried. One pixel is one unit on the wall and a CS 1.6 player stands 72 units tall, so the square lands a little below head height. The palette uses 231 of its 256 slots, spent almost entirely on greys, and nothing in the frame is transparent. The file is 6,296 bytes, comfortably inside the 16 KB tempdecal limit. Two internet shortcut files came in the same archive.