There is a list of MyBB themes at MyBB Mods.
The 1.6 Documentation is no longer maintained and some information may be outdated.
The MyBB 1.6 series reached end of life on October 1, 2015.
This means there will be no more security or maintenance releases for these series and forums running these versions of MyBB may be at risk of unfixed security issues. All administrators are strongly encouraged to upgrade their forums to the latest release of MyBB as soon as possible.