Just as other members had already mentioned, you have to be a junior member or cooper member to be able to post images on BitcoinTalk. But nevertheless, if you have a post  that contains an image you might want to share for further understanding, then you can upload your image on Talkimg.com( Bitcoitalk image hosting site),  then copy and  drop the image link along side your post. A member may be willing to help your repost the image or you can request for a member to assist you.