TGA
The Targa format games grew up on.
Where it came from
TGA (Targa) was created by Truevision in 1984 for their TARGA graphics cards, aimed at professional video. It became a staple of MS-DOS and early Windows games because it handled alpha transparency when almost nothing else did.
Quake, Doom and countless 3D engines shipped textures as TGA. Today it lingers in 3D tools and legacy game assets.
How it works
TGA supports uncompressed and RLE-compressed pixels, indexed or true-color, with an optional alpha channel. Its header is tiny and the format is easy to stream.
UWC converts TGA → PNG/JPEG on the server, since browsers do not decode it natively.