Initial structure

osu.Game.Rulesets.Mania.Tests/Skinning/ManiaSkinnableTestScene.cs

@@ -31,6 +31,7 @@ namespace osu.Game.Rulesets.Mania.Tests.Skinning
         {
             typeof(ManiaRuleset),
             typeof(ManiaLegacySkinTransformer),
+            typeof(ManiaSettingsSubsection)
         };
 
         protected override Ruleset CreateRulesetForSkinProvider() => new ManiaRuleset();

osu.Game.Rulesets.Mania.Tests/Skinning/TestSceneStageBackground.cs

@@ -0,0 +1,35 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Game.Rulesets.Mania.Skinning;
+using osu.Game.Rulesets.Mania.UI.Components;
+using osu.Game.Skinning;
+
+namespace osu.Game.Rulesets.Mania.Tests.Skinning
+{
+    public class TestSceneStageBackground : ManiaSkinnableTestScene
+    {
+        public override IReadOnlyList<Type> RequiredTypes => base.RequiredTypes.Concat(new[]
+        {
+            typeof(DefaultStageBackground),
+            typeof(LegacyStageBackground),
+        }).ToList();
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            SetContents(() => new SkinnableDrawable(new ManiaSkinComponent(ManiaSkinComponents.StageBackground), _ => new DefaultStageBackground())
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                RelativeSizeAxes = Axes.Both,
+                Width = 0.5f,
+            });
+        }
+    }
+}

osu.Game.Rulesets.Mania/ManiaSkinComponent.cs

@@ -39,6 +39,7 @@ namespace osu.Game.Rulesets.Mania
         HoldNoteHead,
         HoldNoteTail,
         HoldNoteBody,
-        HitExplosion
+        HitExplosion,
+        StageBackground
     }
 }

osu.Game.Rulesets.Mania/Skinning/LegacyStageBackground.cs

@@ -0,0 +1,11 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics.Containers;
+
+namespace osu.Game.Rulesets.Mania.Skinning
+{
+    public class LegacyStageBackground : CompositeDrawable
+    {
+    }
+}

osu.Game.Rulesets.Mania/Skinning/ManiaLegacySkinTransformer.cs

@@ -81,6 +81,9 @@ namespace osu.Game.Rulesets.Mania.Skinning
 
                         case ManiaSkinComponents.HitExplosion:
                             return new LegacyHitExplosion();
+
+                        case ManiaSkinComponents.StageBackground:
+                            return new LegacyStageBackground();
                     }
 
                     break;

osu.Game.Rulesets.Mania/UI/Components/DefaultStageBackground.cs

@@ -0,0 +1,11 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics.Containers;
+
+namespace osu.Game.Rulesets.Mania.UI.Components
+{
+    public class DefaultStageBackground : CompositeDrawable
+    {
+    }
+}