I use the stripped theme for a private gallery. Now when i browse to index.php and i'm not logged in, the page is almost empty (just title of gallery, login link...) and i would like to add an image there. In which template file i can do this?

Another possibility would be to forward to the login page automatically.

Can i add something like:

{if !USER_IS_LOGGED_IN} <=== How can i determine, if a user is logged in?
<div id="placholder_image">
<img src="...">
</div>
{/if}

or

Can i add something like:

{if !LOGGED_IN}
FORWARD TO LOGIN <=== How can i forward to another page
{/if}

Is there somewhere an API description, which code/variables i can use in themes?

Best regards
TheChief