It would be really awesome if you made it x4 bigger. Quite a project though. I think you should go for it!
Limited color might actually play well depending on what colors are selected... hints of a hue rather than full saturation so as not to distract from the incredible detail you've worked so hard on... I do like it as is though...
I'm really impressed. I am rarely impressed so take that for what it's worth. I think it works well without colour. No need to compromise an already great piece.