If you're asking for the near-infinite sprawl of the older games, then no, there aren't any mods that do that sort of thing. The game has several mechanisms by which it discourages this sort of thing, most notably the Happiness system; since cities can't generate enough happiness through buildings to completely offset the population unhappiness indefinitely, you're effectively limited to a number of cities based on the number of luxuries (which are finite), the policies you choose, the Wonders you build, and the size at which your cities top out.
So if you wanted to make incredibly huge empires with no real downside, what you'd need is a mod that changes a lot of variables to make Happiness not be an effective limit. And since that sort of game would not be fun at all for most of us (since you'd wipe the floor with the AI), no one makes mods like that. You could always do it yourself, though.