public static void RegisterControl<T>(
    ImageSource icon
)
    where T : XRControl, new()

Public Shared Sub RegisterControl(Of T As {XRControl, New})(
    icon As ImageSource
)

using DevExpress.Xpf.Core.Native;
using DevExpress.Xpf.Reports.UserDesigner;
using DevExpress.XtraReports.UI;
using System.Windows;
using System.Windows.Media;
//...

public class ProgressBar : XRControl { /* ... */ }
//...

public partial class MainWindow : Window {
    public MainWindow() {
        InitializeComponent();

        ImageSource icon = WpfSvgRenderer.CreateImageSource(new Uri("path/to/progress_bar.svg"));
        ReportDesigner.RegisterControl<ProgressBar>(icon);
    }

    private void Window_Loaded(object sender, RoutedEventArgs e) {
        reportDesigner.OpenDocument(new XtraReport());
    }
}

Imports DevExpress.Xpf.Core.Native
Imports DevExpress.Xpf.Reports.UserDesigner
Imports DevExpress.XtraReports.UI
Imports System.Windows
Imports System.Windows.Media
'...

Public Class ProgressBar ' ...
    Inherits XRControl

End Class
'...

Partial Public Class MainWindow
    Inherits Window

    Public Sub New()
        InitializeComponent()

        Dim icon_Renamed As ImageSource = WpfSvgRenderer.CreateImageSource(New Uri("path/to/progress_bar.svg"))
        ReportDesigner.RegisterControl(Of ProgressBar)(icon_Renamed)
    End Sub

    Private Sub Window_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
        reportDesigner.OpenDocument(New XtraReport())
    End Sub
End Class