It does indeed look very awkward without images but the rules for WP:NFC explicitely state that: The use of non-free media in lists, galleries, discographies, and navigational and user-interface elements is usually unacceptable for failing the test for significance (criterion #8). And right now, I don't see any possibility of Madlax character list being a special case exempt from it. ( Of course, other anime character lists do this all the time but the fact is: it is against the guidelines. And it may even cost the main article its featured status on which I've spent almost year of hard work...
Addressing your suggestion, it is indeed possible to just revert the removal of the images but that won't deal with the source of the problem: the unacceptability of such act under Wikipedia policies, which in turn, stems from the US fair use and copyright laws. Unfortunately, there is very little I can do about the latter, so anyone who'd remove the images again will be formally right AND it will eventually lead to an edit war which is an unconditionally bad development.
Don't think that I don't understand your concern. I too, hate character lists without character portraits and a thought of my favourite anime series having one pains me to no end. But it's just the way Wikipedia is. Being the most popular educational site on the web sadly comes with a price tag. (  ☭