That would be relatively labor-intensive, though, not to mention resource-inefficient (you'd end up having multiple tilesets per lighting situation).
I personally think a pixel shader would be ideal, since it would allow you to customise to a high degree the night look (or other lighting moods, such as, eg, red warning lighting). You could also fade the edges of the screen to black, etc. A pixel shader would even allow you to gradually shift from day to night relatively convincingly.