Some portion of optimizations:

* Clear outgoing packet queue after player disconnect
* Disable sleep between chunk saving
* Put 2x4096 bytes instead 2048x4 bytes for region file aligment
* Using map to search player by name instead iterating over all players
* Some tweaks for decorations (item frames, maps)

src/main/java/org/bukkit/craftbukkit/map/CraftMapRenderer.java

@@ -1,6 +1,9 @@
 package org.bukkit.craftbukkit.map;
 
 
+import java.util.Map;
+import java.util.UUID;
+
 import org.bukkit.Bukkit;
 import org.bukkit.entity.Player;
 import org.bukkit.map.MapCanvas;
@@ -8,6 +11,8 @@ import org.bukkit.map.MapCursorCollection;
 import org.bukkit.map.MapRenderer;
 import org.bukkit.map.MapView;
 
+import net.minecraft.world.storage.MapData;
+
 public class CraftMapRenderer extends MapRenderer {
 
     private final net.minecraft.world.storage.MapData worldMap;
@@ -32,14 +37,14 @@ public class CraftMapRenderer extends MapRenderer {
             cursors.removeCursor(cursors.getCursor(0));
         }
 
-        for (Object key : worldMap.playersVisibleOnMap.keySet()) {
+        for (Map.Entry<UUID, MapData.MapCoord> key : worldMap.playersVisibleOnMap.entrySet()) {
             // If this cursor is for a player check visibility with vanish system
-            Player other = Bukkit.getPlayerExact((String) key);
+            Player other = Bukkit.getPlayer(key.getKey());
             if (other != null && !player.canSee(other)) {
                 continue;
             }
 
-            net.minecraft.world.storage.MapData.MapCoord decoration = (net.minecraft.world.storage.MapData.MapCoord) worldMap.playersVisibleOnMap.get(key);
+            MapData.MapCoord decoration = key.getValue();
             cursors.addCursor(decoration.centerX, decoration.centerZ, (byte) (decoration.iconRotation & 15), decoration.iconSize);
         }
     }

src/main/java/org/spigotmc/CaseInsensitiveHashingStrategy.java

@@ -0,0 +1,18 @@
+package org.spigotmc;
+
+import gnu.trove.strategy.HashingStrategy;
+
+class CaseInsensitiveHashingStrategy implements HashingStrategy<String> {
+	private static final long serialVersionUID = -9212222772914758878L;
+	static final CaseInsensitiveHashingStrategy INSTANCE = new CaseInsensitiveHashingStrategy();
+
+    @Override
+    public int computeHashCode(String object) {
+        return object.toLowerCase().hashCode();
+    }
+
+    @Override
+    public boolean equals(String o1, String o2) {
+        return o1.equalsIgnoreCase(o2);
+    }
+}

src/main/java/org/spigotmc/CaseInsensitiveMap.java

@@ -0,0 +1,15 @@
+package org.spigotmc;
+
+import gnu.trove.map.hash.TCustomHashMap;
+import java.util.Map;
+
+public class CaseInsensitiveMap<V> extends TCustomHashMap<String, V> {
+
+    public CaseInsensitiveMap() {
+        super(CaseInsensitiveHashingStrategy.INSTANCE);
+    }
+
+    public CaseInsensitiveMap(Map<? extends String, ? extends V> map) {
+        super(CaseInsensitiveHashingStrategy.INSTANCE, map);
+    }
+}