Well, there is a command for dynamic shadows but I'm not sure it gives a particularly good result.
Aside from that, I don't believe there really are any commands that are going to make any real difference to the graphical quality.
Though you can turn on AA by altering your graphic card settings. There is also a mod that has bloom, as well as one offering high res textures for ATCS. Have a look in 'Mods' section of the forums under 'Non-Gameplay Changing'.
But yeah, it is the idTech 3 engine, this is all you get without heavy modification.