I think my memory concerns are over, halved all texture jpg's, replaced the roofs by some snowed roofs, so I could loose the extra nodes to get snow on the roofs, and also found that the only tree still had a bark texture of 10MB, which is now some 50kB. I filled half the city with what houses I had, but for variation I'd have to make some more. Just rendered a crop of a total of 4000x2000px, still without soft shadows and low clouds to see how it went. It went quite ok. Will be updated...
By the way, I have permission to use the Garden of Eternity for the contest, so I'll give it some priority. Hope I make it in time...