first of all, run in "normal" mode, then tweak. Running in lowest mode is stupid, you loose all the visual quality but gain little performance.
To keep image quality but gain performance, try these:
r_lodbias 1
cg_drawicons 0
cg_noprojectiletrail 1
cg_gibs 0
r_dynamiclight 0
cg_marks 0
r_fastsky 1
s_loadas8bit 1
com_hunkmegs 96
s_khz 11
I've got a whole bunch for Quake 3 games, but they're all in my .cfg and I haven't written down what they were.