Of course. The icon with the Marvel sprites is already down. Frankly, I made barely any of these icons (yeah, a great admin I am) and it was so long ago it just slipped, especially that I assumed it wasn't the case. And especially that we had that kind of a problem once - we forgot the credits. And that case was solved, all were listed in the topic announcing the start of our forum. It might have been my mistake not to sticky it. But we do not claim ownership to any of the sprites we didn't create, I can assure you of that.
Well, I can't find the topic about that situation, created by one of you (I can't remember who exactly) around the end of April 2010 i think (I corrected the credits at 1st of May 2010, our former admin completed it with credits for backgrounds later that month). I thought the case was closed because after that there were no additional complaints.
About the sprites used without permission, we'll get rid of them as soon as we locate them. It might be a little bit hard as it's from 2-3 years ago mostly, so we would very much appreciate if you (or anyone) could specify which sprites are to be taken down. As for the sprites that are from the spriters from outside our forum and are credited, I do not comprehend why the case should be brought up the second time. If there are some not listed in the credits however, it's our mistake which shall be corrected.
I'm afraid later this week it may take more time for us to answer - it happens to be the time where I have to leave for four days and Yoh may have more to do at his job. Unless we finish tomorrow. The sooner the better.