Personally, I would love to see some more customization available.
I have seen two basic approaches to online games that allow symbols. The first is to provide a standardized set of symbols that players can choose from. That is the most common. The second is a mix of that and allowing the player to develop custom symbols through a editor provided within the game.
APB Reloaded would be a good example of that. In those games, the editor usually becomes a mini-game and major feature of the game.
The problem is that such things are resource gluttons; from a program, staffing, and overall financial standpoint. For one thing, if you provide an editor or allow for player uploadable content, you have to provide for policing trademark violations. If you're going to provide all those features, you wind up charging a lot more for subscriptions, you make it a lot harder to progress as a non-subscriber, and you may even resort to charging a whole lot more than we currently pay in points for ever single upgrade . . . all in an effort to get more real world money out of us to support the game.
Not saying DF is a bad game, on the contrary, it is a great game. Still, you get what you pay for. If Zup wants to start offering us all the luxury features, he will be forced to pass the cost of those features along to us.