You can use imgur.com and copy the BBcode to the right hand side once uploaded, then paste that into a reply (Just below the BBcode, select "Large Thumbnail" before copying the BBcode. This will allow users to see a regular sized version of the picture on the forum, and if they click it, the full size!) There are other ways with other online image hosting services - but I prefer Imgur, it's simple and quick to use. No adverts and no sign up to upload (You can sign up if you like, to save your photo's onto your account).