Greetings!
I made the maps for -me- (against "A.I." players), so each was designed to -my- preference at the time of creation. The MegaHispaniola and MegaJamaica maps are somewhat largish, deliberately so, because at the time I made them, I was specifically interested in the logistical challenges of huge amounts of space with tons of other tribes. The labyrinth map was made much smaller but again with a deliberate logistical issue in that the map itself is a bit of a puzzle in several ways. Specials are missing from -all- maps which I create because I don't like them. I'd rather that the difference in performance between tribes on similar terrain (or in same starting positions across multiple games) be only skill at terrain alteration / transformation choices.
I'm not quite sure what "a natural feeling" could possibly be in a FreeCiv map. The Hispaniola map is actually derived from an elevation picture which I will embed inline below. I "flattened" that image to 7 colors, blurred it a bit to ensure that it would translate to square tiles well, then saved it in PPM format and programmatically converted the PPM image to a FreeCiv terrain layer map. FreeCiv doesn't provide a third dimension (height) so in trying to demonstrate height one could either place a single mountain tile, for instance, where the real elevation picture shows a large area occupied by one mountain, or one could use many mountain tiles to show the entire 2D area which is occupied by that one mountain. I chose the latter method as being more representative of the actual land in a 2D view (looking down from above as it is in the original elevation image.)
The screenshot I posted originally of the MegaHispaniola map is showing a section that is just below the center of the original image. The two inland lakes are visible in both pictures. The "mountains" of Hispaniola may not actually be all that mountainous, but within FreeCiv there are very few tile choices (seven, basically) that indicate elevation. So I used mountain tiles for the highest areas of elevation on the map. The terrain may seem unnatural but it's actually a pretty close match by
elevation.
Attached is another map, a very small one at not even 3,000 tiles. On the other hand... the land is a spiral strip and a warrior unit walking from the beginning to the end of the spiral would take roughly 1,270 turns while the MegaHispaniola map is only 200 tiles wide by 100 tall.
Despite being quite small, the Spiral Sea map / scenario presents some similar logistical issues as the Wrecktangular Labyrinth map but also adds the problem of long traveling distance for both land and sea units.
Here's a screenshot of the Spiral Sea scenario in play, and the scenario file is attached to this post.