I was pretty frustrated when I learned that my second-hand bought copy of Descent - Journeys in the dark came without the floor tiles needed to play the game. Luckily, I was able to ask a friend who owns the game to give me the different tile layouts and I recreated them.
The tiles are constructed to interlock with a bit of leeway, so this print will possibly still work if your printer is not 100% perfectly adjusted, but it is rather tight still, so maybe you will need to adjust.
After printing, you can either just mark the squares on the tiles, or glue a scan onto it (scan not provided here of course).
These tiles are meant for the 1st edition of Descent, but since many tiles are essentially unchanged in the 2nd edition, you might find a use for them there as well. And of course, these can be used for generic dungeon design :)