There are a Lot of good ideas in the new Civilization III Forum...

[Mark_Everson]

All the ideas aren't applicable to Clash, but many of them are (and a lot of them we've already got in mind ). Those who are interested please check it out, and bring back any ideas that seem especially interesting!

-Mark

[Mikael]

I used to regularly visit the "suggestions for civ3" forum, but now that it's been announced that there will be a civ3, it's getting messy.Far too big, too many independant ideas,...too long to visit!

[manurein]

Among what I've seen on the CivII forum are intensive disussions on the nukes/massiv destruction weapons. As this point should be discussed for Clash at one time or another, it could be a good starting point to see what they say about it.
Also, in the Wonder thread I've seen interesting stuff. Dont misunderstand me : I dont want Civ-like wonders at all, but why not a system of custom "great projects"? Please see the discussions about this point on the Civ3 forum and provide feedback.