Please do not attach images unless you have the consent of the owner/creator of the image.
This goes without saying for most posters, and it certainly isn't the first time the mods have pointed it out, but images downloaded from another website and displayed on the Forums, whether as an attachment or in a post, must be done with the written permission of the image owner. You may otherwise be guilty of image theft, which is more insidious than bandwidth theft (using IMG tags to refer to an image on another site without authorization from the site owner, and also known as direct linking) because in most cases the owner of the image is unaware that a theft has occurred, but in both cases the images are subject to removal by the Forum administrators. Image theft is a copyright infringement, and posters who indulge in this illegal acitivity despite repeated warnings from the mods are jeopardizing their posting priveleges.
If you'd like to show readers an image that's on someone else's site, the best way is to provide a link to the page on which the image appears in context, and the best Netiquette involves linking to that site's home page.
If anyone has questions about this, please don't hesitate to ask. Thanks!