The ebook will be a compilation of Fan facts and trivia. some part of the book i will be using images from DC characters. Would i need to ask permission to dc in order to use the images or do i just need to state that in the copyright section of the book? thanks.
There is no simple yes or no answer, but there are some online tests to help determine whether it is fair use.
Also, you should check the law stack exchange which discuss fair use issues like this: https://law.stackexchange.com/questions/tagged/fair-use
I would check the DC site to see if they have any official statement about granting of such use.
I am not a lawyer, but my guess is that limited use of reduced-size or reduced quality images is acceptable as fair use as long as it doesn't detract from the property's economic value.
I think it would help to mention on the copyright page that the images were copyrighted and (often) trademarked by DC Comics.
Often with fair use, even though a publisher may feel that the use of the images constitutes fair use, they may seek permission anyway just to avoid the possibility of lawsuit. I'm guessing that DC comics might refuse permission as a blanket rule though....