Kiwanis Park at Geiger Point (1313 Melbourne Causeway, Melbourne, FL 32901) was a 'backup' at a recent elopement ceremony. Like Douglas park, it's a pretty small place but has some hidden areas underneath the bridge that give it possibilities. Might be worth a scout.
It is basically underneath the bridge from Melbourne to the beaches, so the views are pretty awesome.
From reading the reviews I can see that it's used by pro photographers.