ok, here is the rendercube script:

Code:
var cuberesolution=256; // set up the resolution of the cube here

var cubeposition[3]=0,0,200; // set up the position of the cube here
var west[3]=180,0,0;
var north[3]=90,0,0;
var east[3]=0,0,0;
var south[3]=-90,0,0;
var down[3]=90,-90,0;
var up[3]=90,90,0;

function rendercube()
{
video_set(cuberesolution,cuberesolution,32,0);
camera.arc=90;
vec_set(camera.x,cubeposition);
vec_set(camera.pan,west);
wait(1);
_sshot();
vec_set(camera.x,cubeposition);
vec_set(camera.pan,north);
wait(1);
_sshot();
vec_set(camera.x,cubeposition);
vec_set(camera.pan,east);
wait(1);
_sshot();
vec_set(camera.x,cubeposition);
vec_set(camera.pan,south);
wait(1);
_sshot();
vec_set(camera.x,cubeposition);
vec_set(camera.pan,down);
wait(1);
_sshot();
vec_set(camera.x,cubeposition);
vec_set(camera.pan,up);
wait(1);
_sshot();
}
on_r=rendercube;

i am not 100% sure if all directions are set up correctly. the beta watermarks are a bit annoying and unfortunately the video_set command isn't available in the non-beta version.

if you press r, 6 screenshots will be generated. nothing should move in your level while rendering the cube because there is a wait after rendering each side. copy all screenshots next to each other (in the order 0-1-2-3-4-5) into a new image in your image editing program and save it as <yourcubename+6.tga>.

(if you use this cube for a sky you shouldn't use a z offset in the sky definition because this will lead to distortions.)