Do you want to have your tags rendered in Visual tab of JBoss Tools XHTML editor or you mean somthing else?
Yes, I would want that. I believe that would be natural. We use Tag (Source) Files, so the visual tab should naturaly render it correctly. The mais problem is how to add the tag to the pallete.
Well, if you are using tag files instead of TLD/Facelet libs then you can't import it to JBoss Tools Pallete but you can add your tags manually. See http://docs.jboss.org/tools/3.1.0.GA/en/jsf/html/palette.html#PaletteEditor
But this won't make the visual editor render your tags from Pallete. You will have the DnD feature available only. Please try http://docs.jboss.org/tools/3.1.0.GA/en/jsf/html_single/index.html#vpe_templating for your case.