If you call that 'not much detail' you need your head examined. I think it's a stunner.
The texture you've used for the forests
The texture you've used for the sea
The organic design of the city - well..ok the building shapes are similar but there are so many of them, it must have required a lot of patience (which I certainly don't have) to draw them all.
The only thing I'd say is out of keeping with the style you've used is the pixelly texture of the grasslands (but that would depend on the scale of printing - it would look good at a smaller scale). I think it's utterly superb and am at a loss as to suggestions as to how you could improve it.