Made the Image class static.

src/ImageSharp/Image/Image.Create.cs

@@ -10,7 +10,7 @@ namespace ImageSharp
     /// <content>
     /// Adds static methods allowing the creation of new images from given dimensions.
     /// </content>
-    public sealed partial class Image
+    public static partial class Image
     {
         /// <summary>
         /// Create a new instance of the <see cref="Image{TPixel}"/> class with the given height and the width.

src/ImageSharp/Image/Image.Decode.cs

@@ -15,7 +15,7 @@ namespace ImageSharp
     /// <content>
     /// Adds static methods allowing the decoding of new images.
     /// </content>
-    public sealed partial class Image
+    public static partial class Image
     {
         /// <summary>
         /// By reading the header on the provided stream this calculates the images format.

src/ImageSharp/Image/Image.FromBytes.cs

@@ -13,7 +13,7 @@ namespace ImageSharp
     /// <content>
     /// Adds static methods allowing the creation of new image from a byte array.
     /// </content>
-    public sealed partial class Image
+    public static partial class Image
     {
         /// <summary>
         /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given byte array.

src/ImageSharp/Image/Image.FromFile.cs

@@ -14,7 +14,7 @@ namespace ImageSharp
     /// <content>
     /// Adds static methods allowing the creation of new image from a given file.
     /// </content>
-    public sealed partial class Image
+    public static partial class Image
     {
         /// <summary>
         /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given file.

src/ImageSharp/Image/Image.FromStream.cs

@@ -15,7 +15,7 @@ namespace ImageSharp
     /// <content>
     /// Adds static methods allowing the creation of new image from a given stream.
     /// </content>
-    public sealed partial class Image
+    public static partial class Image
     {
         /// <summary>
         /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given stream.