*sigh* i was referring to choli's suggestion that there be an option in the user cp. It seems a bit unnecessary to add all that into the database just for the sake of choosing.
I say just make it launch in _blank like the rest of the links in postbit.
Or maybe have it open a page with the mybb template with an iframe in the middle that has the url of the relevant attachment.php? That way it would show images/text on the page and pop up other miscellaneous downloads, and you wouldn't forget your were in mybb. Just thought of that... just an idea
I prefer _blank though