Raic,

At this size you can charge for admission for those who want to play :0.

I think I can push 18x36 to 600dpi in which you could double or triple the size without losing too much detail. With 3 or 4 layers my system can handle it. But to be on the safe side 300 dpi to start. The sketch of Amon Sul was done on 8" x 12" paper and scanned at 300 dpi so if that gives a good scale to work with.

Thanks

Rigg