I found this map https://gamebanana.com/maps/70608 - gms_beached. It has a beach, small forest and underground cave system. Thought it might be worth a look?
Speaking too a few of the regulars playing stranded, I feel like a new bigger map might allow for more development of the server allowing the regulars to explore and not get bored of the game mode and is also big enough to keep new players intrigued long enough for them to get excited about the game mode

Hope this is of some use as stranded was and is an awesome game mode, it just needs a bit more going on to make it epic!