How do I add shaders to custom levels?

If any of the textures you use have normal or specular maps, you can include them in the same place as the diffuse texture, except ending in .normal.png or .spec.png and the game will automatically use them. If you want to have actual custom shaders that's a longer topic, let me know.

function clientcmd12dothepq() {
    commandToClient(LocalClientConnection, '34onthedancefloor');
}