[zork]

This is what I used in oUF_Donut just to play around with templates:

--get the addon namespace
  local addon, ns = ...
 
  --object container
  local tmp = CreateFrame("Frame")
  ns.tmp = tmp
 
  ---------------------------------------------
  -- variables
  ---------------------------------------------
 
  tmp.styles = {}
 
  ---------------------------------------------
  -- template functions
  ---------------------------------------------
 
  --template RegisterTemplateByName
  function tmp:RegisterTemplateByName(name,data)
    tmp.styles[name] = data
  end
 
  --template UnregisterTemplateByName
  function tmp:UnregisterTemplateByName(name)
    tmp.styles[name] = nil
  end
 
  --template GetTemplateByName
  function tmp:GetTemplateByName(name)
    return tmp.styles[name]
  end

If you make your templating object global any addon could use them.

Another way is adding new templating or skinning functions to specific frame meta tables. !BeautyCase does this for example. That way you add functions to the default wow api via progressive enhancement. http://code.google.com/p/rothui/sour...ore/lib.lua#84

local frame = FRAME_BY_GLOBALNAME or CreateFrame("Frame")
local mt = getmetatable(frame).__index
mt.SkinFrame = function(self,name,data)
  --do stuff
end
frame:SkinFrame("name", {})

I'm in no way an expert on that topic but it got the job done for what I needed.