Depending on your focus (is the site to share positives about the celebrities or is it there to ridicule and criticise?), you may find that the celeb's publicists will bend over backwards to provide photos that you can use. If you are going to get paparazzi type images, then I hope you have a legal defense budget.
If you are reporting news, then the images probably don't need releases, but whomever took the photo probably still owns the copyright, so you have a new problem of using them.
In other words, you have not provided nearly enough information of how you plan to use the images for anyone to give you an opinion.
MannMade Digital Video