Using the database dump of this wiki, a little application to parse it, LibreOffice and Photoshop I created a couple of graphs about the development of this wiki:
The file count seems to match very accurately to what Special:Statistics is saying. The number of articles in my graph (~6250) is higher than what this wiki reports (currently 7,688), but that's probably because of how MediaWiki counts articles, i.e. it has some heuristic to exclude short articles or unreachable pages. Redirects should not be included in my number, but I admit I also need to test my software and study the MediaWiki XML logic some more. The reason the data series values don't all start from zero is that a few articles and their histories have been imported from Wikipedia, so while this wiki was started in September 2006 (that's more than eight years ago!), some articles are even older than that.
So anyway, I find these charts encouraging: we're doing great! The edit counts seem to follow an exponential curve, and article and file counts are at least linear, if not exponential too. Next I plan to plot the quantity of registered users. Later on I'd also like to release my app to GitHub or some such source code hosting service.
Are there any other graphs you'd like to examine? I could see what I could do. Also let me know what you think of the current graphs: did anything surprise you, or what's the most interesting fact about them?