+ Surrogator supports ``.png``, ``.jpg`` and ``svg`` files.
+
+ For OpenIDs, use the url-encoded URL + extension as filename, for example
+ replace ``/`` with ``%2F``.
+ The filename for ``http://example.org/~foo`` would be
+ ``http:%2F%2Fexample.org%2F~foo.jpg``.
+