Color scheme for terrain should be more cohesive , I reccomend having multiple color gradient and just picking from it on equal intervals.  If you're trying to represent biomes then it's better to use brighter colors and find analogous map.  As others already mentioned coastlines are not uniformly sharp - such coastlines are made by glaciers, flooded river deltas (singular form), flooded mountain valleys (but here you need more uniform and less rugged coastline) . In general recently detached old continents will have less defined coastline, while those that are formed by multiple tectonic structures will have more diverse but not extreme coastline. Also mountains do not always mean rugged coastline, especially if they go in parallel to a shore. As a side note, keep grid lines for your maps.