Koolk was arrested!!

Intellectual property.

Nexon distributes its client for free, sure, but it (and everything else contained within it, including images, sound files, etc) is still owned by Nexon and it's infringement to host it elsewhere in any other form. Like a png image.

They aren't likely to sue every single person who uses Maplestory images, since there's simply too many of them and Nexon doesn't stand to gain much from doing that, but I'm pretty sure it does technically constitute infringement.

Not saying I'm against it.

All I can say is that the freedom of press overrules IP in many cases, especially when the publication only has the mere intention to inform their readers...