Is it possible to show the images on the customer portal?

The requirement is to show  portal users a photograph of their Company contact person.

In the Company contact's attachment section i have attached a image as an attachment.

Once the portal user clicks on the link to show the companys contact person a visual force opens up to show the contact photo.

The visual force code is as follows:

<apex:page controller="ViewContactImages" showHeader="false"> 
Showing the Image with Id {!mainImage}
<apex:image url="{!URLFOR($Action.Attachment.Download, mainImage)}"/>
</apex:page>

The controller is as follows:

public class ViewContactImages{

    public Id mainImage;
    public Id getMainImage(){
    	system.debug('getting the mainImageId =='+mainImage);
    	return mainImage;
    }
    
    public void setMainImage(Id imageId){
    	this.mainImage = imageId;
    }
    
    public ViewContactImages(){
        mainImage = 
        [select Id from Attachment 
        	where ParentId = :ApexPages.currentPage().getParameters().get('conId')].Id;
    }
}

 When i get into the customer portal and get to the visual page that shud show the image i cannot see the image.

Any heads up appreciated.

Thanks'

Simson