madhouse,

чтобы отобразить рисунок (байтовый массив) конвертер не нужен:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ImageBinding
{
public class DBImage
{
// в БД картинка это байтовый массив
public byte[] Img { get; set; }
}
}

<Window x:Class="ImageBinding.MainWindow"
xmlns=" http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x=" http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Border Height="150" HorizontalAlignment="Left" Margin="31,28,0,0" VerticalAlignment="Top" Width="150"
BorderThickness="2" BorderBrush="Blue">
<Image Name="image1" Source="{Binding Img}" />
</Border>
<Button Content="Bind" Height="33" HorizontalAlignment="Left" Margin="44,203,0,0" Name="button1"
VerticalAlignment="Top" Width="124" Click="onBind"/>
</Grid>
</Window>

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.IO;

namespace ImageBinding
{
/// <summary>
/// Логика взаимодействия для MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}

private void onBind(object sender, RoutedEventArgs e)
{
DBImage img = new DBImage();
img.Img = File.ReadAllBytes("Koala.jpg");
image1.DataContext = img;
}
}
}