I think you could improve on the mono version. A nice feature of the original is the contrast between the white and yellow areas of paint - this has been lost somewhat in the conversion. I used Nik Silver Efex and found that the High Structure preset did a pretty good job of this, as well as emphasising the textures in the paintwork. I also think that you could bring out more detail in the two wall lanterns, by selecting them and lifting the shadows using the Shadow / Highlight control in Photoship.