This is surely one of the greatest responses I've ever seen on the internet. What was the intention with the unused space originally? Did you foresee this moment coming?
When designing a file format, it is always a good idea to plan for enhancements. There were originally 36 bytes of unused space in the 100-byte header of the SQLite 3.0.0 file format, back in 2004 - bytes set aside specifically to deal with unforeseen needs. Over the years, 12 of those bytes have been allocated to various improvements. 24 bytes remain. (I'd prefer not to use them up all at once or on a whim, obviously.)