if you are cgoing to set the file name using a session:
'FileName' => "".$_SESSION['attractionpic'] ."",
make sure the name in the session does not include the extension.
other wise leave the ddefault:
'FileName' => "[FileName]",
if you leave the default as in the above example, you can select the option to rename the new file if it already exists, and the extension will handle the renaming for you.