Setting preview image for Sharepoint 2010 custom web template

I have a custom Sharepoint 2010 Web Template and I would like to set a custom preview image for it in the Sharepoint add site gallery.

Example (I wanna set a custom image for the "Project Template Site" custom web template):

Note: I already tried setting the ImageUrl p开发者_运维知识库roperty of the WebTemplate element (http://msdn.microsoft.com/en-us/library/ff408392.aspx) and it is not working..

I've managed to solve my problem. Apparently the ImageUrl property of the template element only works with relative URLs (and I was trying to set it to an absolute URL).

<WebTemplate
    (...)
    ImageUrl="/_layouts/images/example.PNG" /> <!-- Works -->