One thing I found surprisingly enjoyable when experimenting with large scale ModTer terrain projects was making basins and cliffs (the two make a very neat contrast when put next to each other) though I'm not sure how such would turn out with islands, as I mainly create vast in-land scenarios rather than individual masses of land. It might spice things up a little, you never know.
EDIT: Actually, Gibraltar is a real example of a semi-separate land mass that gets away with most of it consisting of a cliff or two (arguably, a mountain) yet is balanced with a good series of lower plateaus. The British Empire had a good old time fortifying it, so it might be fun to copy.
Very nice server, I look forward to further updates.