diff --git a/file_icon/lib/file_icon.dart b/file_icon/lib/file_icon.dart
index 6189426..9ddaec8 100644
--- a/file_icon/lib/file_icon.dart
+++ b/file_icon/lib/file_icon.dart
@@ -1,16 +1,25 @@
 import 'package:flutter/widgets.dart';
 import 'src/data.dart';
 
+typedef CustomBuilder = Widget? Function(String? key, Icon icon);
+
 class FileIcon extends StatelessWidget {
   final String fileName;
-  final double size;
+  final double? size;
+
+  /// This color will override the color provided from Seti icons
+  final Color? color;
+
+  /// Use this widget to render custom widget by checking the key.
+  /// It returns recognized file extension as a [key], and [icon] widget which will be rendered.
+  /// This can be used to show custom icon when file type is unknown ([key] is null)
+  final CustomBuilder? customBuilder;
 
-  FileIcon(String fileName, {this.size})
-      : this.fileName = fileName.toLowerCase();
+  FileIcon(String fileName, {this.size, this.color, this.customBuilder}) : this.fileName = fileName.toLowerCase();
 
   @override
   Widget build(BuildContext context) {
-    String key;
+    String? key;
 
     if (iconSetMap.containsKey(fileName)) {
       key = fileName;
@@ -26,18 +35,16 @@ class FileIcon extends StatelessWidget {
       }
     }
 
-    if (key == null) {
-      key = '.txt';
-    }
-
-    return Icon(
+    final Icon iconWidget = Icon(
       IconData(
-        iconSetMap[key].codePoint,
+        iconSetMap[key ?? '.txt']!.codePoint,
         fontFamily: 'Seti',
         fontPackage: 'file_icon',
       ),
-      color: Color(iconSetMap[key].color),
+      color: color ?? Color(iconSetMap[key ?? '.txt']!.color),
       size: size,
     );
+
+    return customBuilder != null ? (customBuilder!(key, iconWidget) ?? iconWidget) : iconWidget;
   }
 }