From the yet to be released readme...
* JPEG and TGA support for textures, by popular request. Loading TGA is a
bit faster than PNG as it is raw data and thus does not need to be
decompressed and such.
* Support 8, 24 and 32 bit PNGs with optional transparency and grayscale
using PNG transforms.
* PNG reading process speed substantially increased through removal of
* PNG library uses x86-asm hand tuned version of zlib inffast.c for faster
* Trimmed down PNG library features to include only those necessary for
R1GL to operate.
* JPEG screenshot support, "screenshot jpg".
* More TGA formats understood.
* Point sprite support for particles (gl_ext_point_sprite 1, and place a
particle.png/tga in baseq2).
* gl_pic_formats and gl_texture_formats cvars to choose which image formats
you wish to search for when loading pics (hud icons, skins, etc) or
textures (map textures). A string of "png jpg" will only try loading
additional png and jpg files, the original .pcx or .wal is always tried.
* gl_overbrights, experimental overbright rendering.
* gl_doublelight_entities to restore original "double lighting" of entities
as per the original Quake II ref_gl. Previously known as gl_r1gl_test.
* Optimized how some options are checked each frame for increased speed.