Try adding the @Html.FullPageRefresh() to the view to force a refresh (you need to pass in the property names in the method). This is from memory so the method name might me slightly different.

Frederik

Fredrik is right, do a FullPageRefresh() and it will work.
You can get it to work even wiithout it but then you have to take in count that when EPiServer calls the displaytemplate after you have loaded a image but before you done a fullpage refresh it does not pass in the same thing. It passes in a json-string with information of contentid and so on.
I can show you in code tomorrow (does not have the code here) how we do that for one of our displaytemplates

We have a customproperty that inherit from xhtml and using it's own type of inheritance so not to confuse I have removed all that logic from the example.

First in our displaytemplate we call a extensionmethod to do the logic:

@{
    var htmlValue = @HtmlHelpers.GetInheritXhtmlValue(@ViewData["propertyName"].ToString(), (object)@ViewData["CurrentPage"], Model);
}

@Html.Raw(htmlValue)

Then the extension method looks like this:

public static object GetInheritXhtmlValue(string propertyName, object currentPageOrRef, string propertyValue)
        {
            PageData currentPage = null;

            if (currentPageOrRef == null)
            {
                return string.Empty;
            }

            if (currentPageOrRef is PageData)
            {
               // return PageData-value, ie: the main load of page
                
            }
            else
            {
                //It is a on page edit update of page, then there is a json formated link to the page
                var json = Json.Decode(currentPageOrRef.ToString());
                if (json.contentLink != null)
                {
                    currentPage = ServiceLocator.Current.GetInstance<IContentRepository>().Get<EducationLocationPage>(new ContentReference(json.contentLink));
                    return GetParentPropertyValue(propertyName, currentPage);
                }
            }

            return string.Empty;
        }

Hope this will help someone

Thanks for the answers Fredrik and Henrik. I havent had the time to try out the FullPageRefresh yet. But it surley will atleast please the customer.