I have been lurking this thread for a while but its about time I chipped in. I was pretty involved in the first CWBP and so have some points to make but also I didnt want to steer the new one. Id like to see how it pans out differently this time. But for what its worth here are some items that worked well and that didnt work so well first time around so you can improve or utilize them again.
We had square tiles which I think was good tho people said that as they spanned different lattitudes then on a mercator style projecion the actual physical scale of them was varying across the maps. It was hard to make equal area maps using tiles that span a significant lattitude range.
We used FT and had a height map for the first CWBP. Having a public high res height map for the whole world / area under mapping was useful as you could as a last resort use a procedural mapping system to fill in any holes left by absentee mappers.
The tiles we had were something like 400km or so across and towns within them were usually mapped at a scale that people did them at unrealistic sizes. At 400km per tile a city is about a pixel or two.
It was extremely useful to nail down the format of the thread naming for each tile and city since we admins created a CWBP map indexer out of the threads so that new places mapped got added to an index automatically - see my sig for the link into that. I am not sure whether its still working tho since the site format for threads changed. But the idea that you can scrape the names under a CWBP2 section to create the index is cool.
I made up the overall map of CWBP (the composite of all the mapped places) and I am prepared to do a similar one for the new CWBP2 if nobody else is hankering for that role. That is not making up the shape of the landmass etc but the collection of everybody's work and stitch it together into the mosaic of finished maps. Like this:
Its not too obvious but if you look closely then it has all of the small regions and cities mapped on it too. It has every map that was done for the region on this composite version. Click on it to embiggen.