Feature Layer Icon

Hi All

I am adding feature layers to my site and am trying to change the icon.

In my Service I have basic symbols and am hoping to change them through Manager.  On both my Silverlight and HTML sites after I change the symbol under 'Icon Url' to what I want,  the viewers both still display the basic Icon on the map.

Do I have to change the symbols directly in the .mxd/service?  or is there a way to change it manager?

Thanks