I think going with terracotta is a good idea, but you can make it a bit more varied. There could be different hues of terracotta (eg, where old tiles had to be replaced with new ones), and some buildings could be covered by different materials (important buildings might be given metal sheet roofing, for instance).

One little criticism (and this might just be personal opinion, in which case ignore it), I think the cliffs look very smooth, and not rough enough (compared, for instance, to the areas around the harbour). I really like the shading on them, though.

THW