I've done the following for saving the file size, guess you could do something similar to populate Height and Width.

[InitializableModule]
    [ModuleDependency(typeof(EPiServer.Web.InitializationModule))]
    public class FileInitialization : IInitializableModule
    {
        public void Initialize(InitializationEngine context)
        {
            var eventRegistry =
            ServiceLocator.Current.GetInstance<IContentEvents>();

            eventRegistry.CreatingContent += OnCreatingContent;
            eventRegistry.SavingContent += OnSavingContent;
        }
private void OnSavingContent(object sender, ContentEventArgs e)
        {
            var content = e.Content as MediaData;
            if (content == null || !(content is ISearchableFile))
                return;
            var fs = content.GetFileSize();
            ((ISearchableFile)content).FileSizeInKb = (int)fs;
        }

        private static void OnCreatingContent(object sender, ContentEventArgs e)
        {
            var content = e.Content as MediaData;
            if (content == null || !(content is ISearchableFile))
                return;
            var fs = content.GetFileSize();
            ((ISearchableFile)content).FileSizeInKb = (int)fs;
        }
}

I would go with Erik's approach. Mark Everard has a good example on how to get the dimensions: https://github.com/markeverard/Chief2moro.ImageDataExtensions/blob/master/src/Chief2moro.ImageDataExtensions/ImageBlobUtility.cs

Also, I would add the [Editable(false)] attribute to the properties, as this would be read-only properties.

This is awesome! exactly what I was looking for.

Thanks guys! Thanks a lot!