To do this you would make all the textures you want to be possible in the matrix into a single image. Each picture can be put side by side and up and down to make a rectangle. Load the image and when you prepare matrix texture you put in how many pictures there are across and how many pictures down there are in the image. In set matrix tile you specify which of these pictures you are using in that tile. The pictures are numbered left to write from top to bottom just like how you read English. I hope I haven't rambled. This might help a bit.
autocam off
hide mouse
ink rgb(255,0,0),0
box 0,0,10,10
ink rgb(0,255,0),0
box 10,0,20,10
get image 1,0,0,20,10
cls
sync on
make matrix 1,10000,10000,50,50
randomize timer()
randomize matrix 1,10
prepare matrix texture 1,1,2,1
position camera 5000,get ground height (1,5000,5000)+10,5000
set matrix trim 1,0.08,0.08
do
set matrix tile 1,camera position x()/200,camera position z()/200,1
control camera using arrowkeys 0,0.5,0.5
set matrix tile 1,camera position x()/200,camera position z()/200,2
update matrix 1
position camera camera position x(),get ground height (1,camera position x(),camera position z())+10,camera position z()
sync
loop
Insanity is just a state of mind
