r_customHeight [pixels] - Sets a custom screen height in pixels. The r_mode command must be set to -1 to allow this to work.
r_customWidth [pixels] - Sets a custom screen width in pixels. The r_mode command must be set to -1 to allow this to work.
r_mode [-1,3,4,5,6,7,8] - This setting determines the resolution, as set in the in-game menus under Screen Size (See In-Game Settings section). The mode values are -1 = Custom (see r_customheight, r_customwidth commands), 3 = 640x480, 4 = 800x600, 5 = 1024x768, 6 = 1152x864, 7 =1280x1024 and 8 = 1600x1200.