[haste]

It's quite straight forward to change the texture:

local CPoints = {}
   for index = 1, MAX_COMBO_POINTS do
      local CPoint = self:CreateTexture(nil, 'BACKGROUND')
 
      CPoint:SetTexture[[Interface\AddOns\Path\To\Texture]]
 
      -- Position and size of the combo point.
      CPoint:SetSize(16, 16)
      CPoint:SetPoint('TOPLEFT', self, 'BOTTOMLEFT', index * CPoint:GetWidth(), 0)
   
      CPoints[index] = CPoint
   end
   
   -- Register with oUF
   self.CPoints = CPoints