Crop BDSP Box Wallpapers, re-tile Grass, and fix off-by-one

PKHeX.Core/Saves/Substructures/Gen8/BS/BoxLayout8b.cs

@@ -132,14 +132,14 @@ namespace PKHeX.Core
         {
             if ((uint)box > BoxCount)
                 return 0;
-            return Data[GetBoxWallpaperOffset(box)];
+            return Data[GetBoxWallpaperOffset(box)] - 1;
         }
 
         public void SetBoxWallpaper(int box, int value)
         {
             if ((uint)box > BoxCount)
                 return;
-            Data[GetBoxWallpaperOffset(box)] = (byte)value;
+            Data[GetBoxWallpaperOffset(box)] = (byte)(value + 1);
         }
 
         public ushort StatusPut

PKHeX.Drawing/Names/BoxWallpaper.cs

@@ -29,8 +29,7 @@ namespace PKHeX.Drawing
             5 => B2W2.Contains(version) && index > 16 ? "b2w2" : "bw",
             6 => ORAS.Contains(version) && index > 16 ? "ao" : "xy",
             7 when !GG.Contains(version) => "xy",
-            8 when BDSP.Contains(version) => "bdsp",
-            8 => "swsh",
+            8 => BDSP.Contains(version) ? "bdsp" : "swsh",
             _ => string.Empty,
         };
 

PKHeX.WinForms/Subforms/Save Editors/Gen6/SAV_BoxLayout.cs

@@ -46,11 +46,14 @@ namespace PKHeX.WinForms
                     CB_BG.Items.AddRange(GameInfo.Strings.wallpapernames.Slice(0, 16));
                     return true;
                 case 4 or 5 or 6:
-                    CB_BG.Items.AddRange(GameInfo.Strings.wallpapernames);
+                    CB_BG.Items.AddRange(GameInfo.Strings.wallpapernames.Slice(0, 24));
                     return true;
                 case 7:
                     CB_BG.Items.AddRange(GameInfo.Strings.wallpapernames.Slice(0, 16));
                     return true;
+                case 8 when SAV is SAV8BS:
+                    CB_BG.Items.AddRange(GameInfo.Strings.wallpapernames);
+                    return true;
                 case 8:
                     CB_BG.Items.AddRange(Enumerable.Range(1, 19).Select(z => $"Wallpaper {z}").ToArray());
                     return true;