WatermarkSettings.cs was very limited, but useful. It has been replaced by the concept of plugins in V2. If you're wanting do any kind of watermarking (whether text or image overlays), the new watmark plugin can probably handle it.

Example plugin:

using ImageResizer.Configuration;
using ImageResizer.Resizing;
using System.Collections.Generic;
using ImageResizer.Plugins;

namespace MyCode.MyPlugins {
  /// <summary>
  /// Writes the text specified in the 'sample' querystring value
  /// </summary>
  public class SamplePlugin : BuilderExtension, IPlugin, IQuerystringPlugin {


    protected override RequestedAction OnProcess(ImageState s) {
        return base.OnProcess(s);
        // If we wanted to modify the querystring or settings before the pipleine started, 
        // we could do it here (like the ModifySettings method of WatermarkSettings.cs in V2)
    }

    protected override RequestedAction RenderOverlays(ImageState s) {
        // Get 'sample' from the querystring
        string sample = s.settings["sample"]; 

        //Don't try to draw the string if it is empty, or if this is a 'simulation' render
        if (string.IsNullOrEmpty(sample) || s.destGraphics == null) return RequestedAction.None;

        //Let's use Arial, and make sure the text fits inside the bitmap width.
        System.Drawing.Font font = new System.Drawing.Font("Arial", 
            (float)(s.destBitmap.Width / (sample.Length * 1.5f)), System.Drawing.GraphicsUnit.Pixel);

        //Draw the text at the top left corner of the resulting image.
        s.destGraphics.DrawString(sample, font, System.Drawing.Brushes.Black, 0, 0);

        return RequestedAction.None;
    }

    public SamplePlugin() { 
    }

    Config c;
    public IPlugin Install(Config c) { //Allows '<add name="MyCode.MyPlugins.SamplePlugin" />' to work
        c.Plugins.add_plugin(this);
        this.c = c;
        return this;
    }

    public bool Uninstall(Config c) { //Allows '<remove name="MyCode.MyPlugins.SamplePlugin" />' to work
        c.Plugins.remove_plugin(this);
        return true;
    }

    public IEnumerable<string> GetSupportedQuerystringKeys() {
        return new string[] { "sample" }; //So the pipeline knows to handle image requests that use this querystring key
    }
  }
}