1.) New icons - also called cameos, you can make them with paint shop pro or a program like it. Blade has a good tutorial on that,
http://www.mysanctuary.demon.co.uk/icontut.zip
He has everything you need to know there.
2.) Voxels are used for vehicles and aircraft ingame use. You can create them by using Will's VXL editor. Vxls also need HVAs to run properly in game. Searching the web will produce much better tutorials than i can write here. Also, like catull said,search these forums.
Good luck.