Clean install of ML

I currently have 10.6 installed. How is it best to perform a clean install of ML? Clean install SL and then perform the upgrade to 10.8 at first boot, or simply clean install ML, without reinstalling SL? I'm asking this because I noticed that after performing a clean install of Lion (not upgrading from SL), the wallpapers on SL were missing, so I was wondering what if wallpapers weren't the only thing that was missing.