The only way on LLama's server seems to be creating the players then on the first or second turn set them to run AI from then on.
There are pros and cons. The AIs will be setup abit better than they would be by random AI. But unforunately one of you will know the settings they are using. You could ask if someone here would step into the game and set them up, then set them to AI and quit. That way it would be a surprise.
OR there are pre-created games on my server.
http://www.dom3minions.com/HostedGames.htm
For just AI's added Id recommend vsAI games. The pros and cons are that they are randomly created (so some dumb settings might get used). On the other hand they are allied with each other, and can use more creation points than the other method which can make them stronger. Oh and its direct-connect instead of pbem in case that was important.
OR you can be a server on your own to make best use of all options. The advantage it more power than either of the other two methods, the drawback is a fairly heavy learning curve in order to get it.