The 2.0 fimware for the Cybook and Opus have new thumbnails for epub files.
They use the .thn extension and it is append after the .epub extension. This is
unlike the _6090.t2b
thumbnails which use the book name without the extension
and _6090.t2b
appended to it. I have yet to start figuring out this new format
but at first glance it looks to be similar to the _6090.t2b
files.
What I have found is, if a _6090.t2b
file is present that will be used and the
.thn file will not be generated and the _6090.t2b
will be used as the
thumbnail. However, if both the _6090.t2b
and .thn are present then the .thn
will be used.