Well..... there are a few tower addons out there angusjm... but I think ofp.cz is still underwater ;D and the addon depot around here is still under renovation it would seem....
But, you should be able to place the three, or is it four?, towers that are available in game through your mission editor.. you might have to have all of the editor upgrades and object files to have access to every one in your editor.. but they're out there...
If you have 1.75 there is an editor uprade for that out also..
hope this helps ya some
*EDIT* Damn you LCD... I have to learn to type faster.. LOL*EDIT* ;D ;D