Well the tube can be useful when you dump everything out in the rain onto the grass to find the matches...one guy had a tube with morse code on it, may not be useful but was way cool!

Now as for the sheath I found that a leatherman micra, the everlasting brass striker that Tom (TAH) shows and some tinder in a small plastic bag fits into the stone stower bit, (I never use the stone, just out it away somewhere).
Oh and wax the sheath, I use Snowseal but there are many different options, add some extra paracord to it and you are good to go.

In the tube I keep more tinder, a compass (removeable one), matches, safety pins, hooks, sinkers, swivels, needles, theard, fishing line (more line is wrapped around the handle under the paracord) duct tape, match striker...think that's it.