public abstract class ImageTileSource :
    MapDependencyObject,
    IImageTileSource,
    ITileItemSourceProvider

Public MustInherit Class ImageTileSource
    Inherits MapDependencyObject
    Implements IImageTileSource,
               ITileItemSourceProvider

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:DXMapInMemoryTileProvider"
        xmlns:dxm="http://schemas.devexpress.com/winfx/2008/xaml/map" 
        x:Class="DXMapInMemoryTileProvider.MainWindow"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <dxm:MapControl>
            <dxm:ImageLayer x:Name="imageLayer"/>
        </dxm:MapControl>
    </Grid>
</Window>

using DevExpress.Xpf.Map;
using System;
using System.Globalization;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;
namespace DXMapInMemoryTileProvider {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
            ImageTileDataProvider tileDataProvider = new ImageTileDataProvider();
            tileDataProvider.TileSource = new SimpleTileGenerator();
            this.imageLayer.DataProvider = tileDataProvider;
        }
    }
    public class SimpleTileGenerator : ImageTileSource {
        Random rnd = new Random();
        public override string Name => nameof(SimpleTileGenerator);
        public override ImageSource GetImageSource(long x, long y, int level, Size size) {
            DrawingVisual drawingVisual = new DrawingVisual();
            using (DrawingContext drawingContext = drawingVisual.RenderOpen()) {
                FormattedText text = new FormattedText($"{x}:{y}:{level}", new CultureInfo("en-us"),
                                     FlowDirection.LeftToRight, new Typeface("Arial"), 14, Brushes.Black);
                drawingContext.DrawRectangle(new SolidColorBrush(Color.FromArgb(128, (byte)rnd.Next(255),
                                                                        (byte)rnd.Next(255), (byte)rnd.Next(255))), null, 
                                                                        new Rect(new Point(), size));
                drawingContext.DrawText(text, new Point(5, 5));
                drawingContext.Close();
            }
            RenderTargetBitmap bmp = new RenderTargetBitmap((int)size.Width, (int)size.Height, 96, 96, PixelFormats.Pbgra32);
            bmp.Render(drawingVisual);
            return bmp;
        }
        protected override MapDependencyObject CreateObject() {
            return new SimpleTileGenerator();
        }
    }
}

Imports DevExpress.Xpf.Map
Imports System
Imports System.Globalization
Imports System.Windows
Imports System.Windows.Media
Imports System.Windows.Media.Imaging
Namespace DXMapInMemoryTileProvider
    Public Partial Class MainWindow
        Inherits Window
        Public Sub New()
            InitializeComponent()
            Dim tileDataProvider As ImageTileDataProvider = New ImageTileDataProvider()
            tileDataProvider.TileSource = New SimpleTileGenerator()
            Me.imageLayer.DataProvider = tileDataProvider
        End Sub
    End Class
    Public Class SimpleTileGenerator
        Inherits ImageTileSource
        Private rnd As Random = New Random()
        Public Overrides ReadOnly Property Name As String
            Get
                Return NameOf(SimpleTileGenerator)
            End Get
        End Property
        Public Overrides Function GetImageSource(ByVal x As Long, ByVal y As Long, ByVal level As Integer, ByVal size As Size) As ImageSource
            Dim drawingVisual As DrawingVisual = New DrawingVisual()

            Using drawingContext As DrawingContext = drawingVisual.RenderOpen()
                Dim text As FormattedText = New FormattedText($"{x}:{y}:{level}", New CultureInfo("en-us"), FlowDirection.LeftToRight, New Typeface("Arial"), 14, Brushes.Black)
                drawingContext.DrawRectangle(New SolidColorBrush(Color.FromArgb(128, CByte(rnd.[Next](255)), CByte(rnd.[Next](255)), CByte(rnd.[Next](255)))), Nothing, New Rect(New Point(), size))
                drawingContext.DrawText(text, New Point(5, 5))
                drawingContext.Close()
            End Using
            Dim bmp As RenderTargetBitmap = New RenderTargetBitmap(CInt(size.Width), CInt(size.Height), 96, 96, PixelFormats.Pbgra32)
            bmp.Render(drawingVisual)
            Return bmp
        End Function

        Protected Overrides Function CreateObject() As MapDependencyObject
            Return New SimpleTileGenerator()
        End Function
    End Class
End Namespace