If I use pictures taken from this site to post on this site. Like here. Do I have to acknowledge where the pics came from each time, or is it ok to recycle material like this from within the site. (I am not referring to taking credit for someone else's work, as I am not professing to be the creator of the pics)
If I understand you correctly, you are referring to images you found on Stack Exchange which you want to repost in another post also on Stack Exchange?
If so, I believe that is fine - especially if you are talking about images which were posted in a question/answer; they would fall under the CC-Wiki. I am not immediately sure about taking someone's profile image, though.
You should, therefore, also link to the source, perhaps in a sub link, each time you post them.