Well, I believe that is a personal preference. I would start with getting snoopy's terrain graphics at a minimum and moving on from their. They are pretty easy to find in the graphic modpacks setion.
As far as rules mods and the like, that is where it is a little more defined by your tastes. Mind you, I don't know a whole lot about all of them out there, pretty much just the major ones. One of the issues Korn was dealing with in the Blitz mod was combat. It sounds like he has it worked out pretty well. The Double Your Pleasure mod is fairly new, but has quite an ambitous set of changes. If Kal-el can pull those off that will be a great mod. I don't know where he stands on it though. The LWC mod, was rather good for a while, but I hear it hasn't been uptated in a while and hasn't had many posts by its creator lately either. The Balancer Mod is something I am a part of. It is pretty much made to balance things out. The latest released version 2.12 doesn't have a lot of military changes, but the one in testing does. 2.15 has major changes to combat set to fix the tank vs spearman problem as well as make military units and choices more interesting and fun. It also addresses issues with resources and terrain stats. They have all been changed in 2.15 which I hope to release shortly. 1.21f put a lot of kinks into it, and we have been trying to iron them out ever since. Oh and we added some buildings, wonders, and governments, as well. Good luck and I hope you find what you are looking for.
