Alak! I've just had an idea

I've gotten a good collection of 12"x12" dungeon tiles, and a smaller batch of cave tiles.   Now it just hit me, I should have some urban tiles too, with various buildings etc.   I suppose I'd have to put a 1" clear space all around the edge, to represent the street.  Although some might only have street on 1-2 sides, to be sure.   Hmmm, I'll have to play around with this.   Suddenly 150 tiles is starting to look like it may eventually not be enough.