How to show the recourse image

It looks like you are missing quotes around the src attribute value:

Dim foto As String = Convert.ToBase64String(r("ImagenP"))
res.Columns.Add(New ResourceColumn("<img src='data:image/jpg;base64," & foto & "' width='150' height='150' /> "))

You might also consider serving the image using a special url. Then you would only use the image URL. This option lets you set caching headers for the image and improve performance.

I answer to myself

Private Sub ParkingDP_BeforeResHeaderRender(sender As Object, e As BeforeResHeaderRenderEventArgs) Handles ParkingDP.BeforeResHeaderRender

Dim htm As String = "<img src=data:image/jpg;base64," & Convert.ToBase64String(e.DataItem("ImagenP")) & " width='150' height='100' /> "
e.Columns(1).Html = htm

End Sub

c#
private void ParkingDP_BeforeResHeaderRender(object sender, BeforeResHeaderRenderEventArgs e)
{
string htm = "<img src=data:image/jpg;base64," + Convert.ToBase64String(e.DataItem("ImagenP")) + " width='150' height='100' /> ";
e.Columns[1].Html = htm;
}

Thanks for posting your solution!

You might also consider serving the image using a special url.??
what do you mean by special url?
save the image in an application folder and address it by link?

Yes, you can serve it as a static file (add it to the application folder). That would be the easiest way.

If that is not possible, you can also serve it from the database by writing the content to the Response as described here:
https://stackoverflow.com/questions/2253228/asp-net-return-image-from-aspx-link

If you add the Expires header it will be cached by the browser and served faster next time:
https://stackoverflow.com/questions/2608739/how-to-specify-http-expiration-header-asp-net-mvciis/6443000#6443000