Add ressources possible with G&K?
AFAIK one sadly can NOT add new icons to ressources in Civ5, so I wonder if this will change with G&K. Are there any infos about this?
I assume you're referring to the small icons on the topbar and used in text - these are "fonticons" in the game's architecture, and they aren't moddable now, correct. It's certainly a common request, and I believe that FXSSSeckman has said he wants to make them moddable, but who knows if that's being worked on for G&K? I don't think anything has been said about changes to modding for the xpac at all.
If they're not using a new DLL for G&K then hopefully we'll be able to see how