Algodoo

There is a script that allows you to make repeating textures on a block easily.

Just make one netherack block and put this script on the script menu of the netherack block (right click -> script menu) and just replace the UPDATE section with

(e)=>{
TEXTUREMATRIX = [1.0, 0.0, POS(0), 0.0, 1.0, POS(1), 0.0, 0.0, 1.0]
}