feat: classic background.

HMCL/src/main/java/org/jackhuang/hmcl/ui/decorator/DecoratorController.java

@@ -139,7 +139,9 @@ public class DecoratorController {
                                         .orElse(null);
                             }
                             if (config().getBackgroundImageType() == EnumBackgroundImage.NETWORK) {
-
+                                image = new Image(config().getBackgroundImageUrl(), true);
+                            } else if (config().getBackgroundImageType() == EnumBackgroundImage.CLASSIC) {
+                                image = newImage("/assets/img/background-classic.jpg");
                             }
                             if (image == null) {
                                 image = loadDefaultBackgroundImage();
@@ -147,7 +149,8 @@ public class DecoratorController {
                             return new Background(new BackgroundImage(image, BackgroundRepeat.NO_REPEAT, BackgroundRepeat.NO_REPEAT, BackgroundPosition.DEFAULT, new BackgroundSize(800, 480, false, false, true, true)));
                         },
                         config().backgroundImageTypeProperty(),
-                        config().backgroundImageProperty()));
+                        config().backgroundImageProperty(),
+                        config().backgroundImageUrlProperty()));
     }
 
     private Image defaultBackground = newImage("/assets/img/background.jpg");