Ok I will attempt to be useful. I figured I could personally use a performance boost so here are some commands I came across. Feel free to experiment with them, some will give you significant fps boost at the cost of visual quality. These combined with the poly packs should give you very playable fps.

These were meant for cs actually but they should also work in ns. Through quick testing of these I went from 37 average fps to 75 (my refresh max). I believe all of these work since I got no errors when executing the config, but some may have no effect on ns itself I suppose. Hope they help you out.

If you have access to the "new" official ns forums (at unknownworlds) then perform a search there, you may find other useful tweaks.

//Sets the maximum size of all textures in the game including walls, player
//models , gun models ect. Default is "512". I use "64". Dont got below "64"
//and always use multiples of 64 , ie 64,128,256,512
gl_max_size "128"

//Another good command for boosting fps , controls rendering quality.The
//following settings are listed in order of speed , first being fastest but poorest
//quality , last being best quality but slowest.
//GL_TEXTUREMODE "GL_NEAREST"
//GL_TEXTUREMODE "GL_LINEAR"
//GL_TEXTUREMODE "GL_NEAREST_MIPMAP_NEAREST"
//GL_TEXTUREMODE "GL_LINEAR_MIPMAP_NEAREST"
//GL_TEXTUREMODE "GL_NEAREST_MIPMAP_LINEAR"
//GL_TEXTUREMODE "GL_NEAREST_MIPMAP_LINEAR"
//GL_TEXTUREMODE "GL_LINEAR_MIPMAP_LINEAR"
//GL_TEXTUREMODE "GL_NEAREST"
GL_TEXTUREMODE "GL_NEAREST"

//Sets the sound quality , 0 being low and best for performance , 1 being
//high and best quality sound. On older computers setting this to 0 can make a
//large difference , but the drop in quality is extremely high
hisound "0"

//A big boost if you find your fps dropping during fire fights. Basically it turns
//off the gun model on screen, so you wont see it. Not good if your a fan of
//custom models but does stop some of the big fps drops in combat. "0" is off , "1" is on
r_drawviewmodel "0"

//Deals with the filling in of cracks between textures or surfaces.Set to "1" and high
//quality will fill them in , set to "0" and fastest it wont , resulting in dots appearing
//between the junctions but more fps
gl_keeptjunctions "0"

//Sets the rendering quality of player models. Can be set at "0" which is best quality but
//slowest, "1" which is medium , and "2" which is worst quality but fastest
gl_playermip "2"

//This set of commands controls displaying of blood.Set to "0" and no blood , improving //fps.Set to "1" and blood will show. I use "0"
violence_ablood "0"
violence_agibs "0"
violence_hblood "0"
violence_hgibs "0"

//Another one that controls texture quality.The lower the number the better quality
//graphics, higher the number the fastest
gl_round_down "100"

//Sets the height of waves in water. 0 being fastest.
gl_wateramp "0"

//Sets the number of decals to be shown. Decals are used to draw bullet holes in walls as
//well as custom tags/sprays.Set to "0" to disable completely , "300" is default
mp_decals "0"

//Sets dynamic lighting(ie reflections ect) , "0" being off and fastest , "1" being on and
//slowest.
r_dynamic "0"

//Similar to dynamic lighting , controls reflections on objects."0" is fastest and off , "1" is
//slowest and on.
r_mirroralpha "0"

//Controls the blending of textures together. "0" is off and looks best but is slowest."1" is
//on and is fastest, however cracks between textures may show.
gl_clear "1"

//Turns dithering on and off. "0" is off , "1" is on. Use 0 for best fps.
gl_dither "0"

//Upper bound on allowable fps I believe.
fps_max "100"
fps_modem "100"

-Cheers