Hi Michael - we can certainly add pre-gen as a category, and anyone is certainly welcome to post up anything they think is appropriate in the wiki.
As you mention though, as 250.org already has a pretty complete wiki for the 1st-gen stuff, I don't want to necessarily spend a whole lot of time duplicating what they already have if we can instead be focusing on what they don't have much of yet. That said, a whole bunch of items in the wiki would likely apply to all gens, so adding "pregen" as an additional category on a number of existing wiki entries and many future ones isn't a bad idea at all.