There is only one file type that uses the .OTZ extension:
OpenLP Theme File
Theme file used by OpenLP, a free application used for developing multimedia content for church worship services; contains settings that give the presentation (an .OSZ file) a certain appearance; may include fonts, text colors, background images, and other display information.
Several OpenLP themes can be downloaded from the OpenLP.org website.
Updated: May 31, 2012