Something I rustled up.
Loads a jpg, creates 50% additional space to right and bottom (in other words, expands the canvas) - saves the result to completed.jpg
Change the position of image in the DrawImage call to position your image appropriately.
Image source = Image.FromFile(@"c:whalloper.jpg");
int width = source.Width + (source.Width /2);
int height = source.Height + (source.Height /2);
// Create a compatible bitmap
Bitmap dest = new Bitmap(width, height, source.PixelFormat);
Graphics gd = Graphics.FromImage(dest);
gd.DrawImage(source,0,0, source.Width, source.Height);
dest.Save(@"c:completed.jpg");
Edit: oops, got a useless device context there in previous version. Unused variable fixed
Current work in progress: Retro Remake of BRUCE LEE, by Datasoft (1984)