New files for the wesnoth.org frontpage portrait rotation
should be made based on the template file in this directory.
I personally recommend using the JPEG format with some
appropriate parameters (and a good exporter program) so that
the images are neither too large in file size, nor look
ugly/blurry/with compression artifacts.

All image files should use the *.jpg extension; otherwise
you'll need to change selector.php.

The selector.php code may be used in place of an actual
image file in CSS, HTML, whatever; the client just tries to
fetch it and the server runs the PHP, delivering one of the
*.jpg files in the directory. However, since some broken
clients may become confused at the .php extension (e.g.
Internet Explorer), it is recommended to append a fake path
component that ends in .jpg, e.g.:

/path/to/selector.php/random.jpg

-- Ignacio