When posting any image, always use thumbnails instead of posting the full size especially when the image is really huge and distorts the frame of the board.
When using Photobucket, all you do is add th_ prior to the filename in the URL. For example http://www.photobucket.com/user/pic.jpg becomes
http://www.photobucket.com/user/th_pic.jpg to display the thumbnail. Imageshack.us you add .th before the file extension. Example
http://img1.imageshack.us/pic1.jpg becomes http://img1.imageshack.us/pic1.th.jpg to display a smaller image. This also helps load
times for people who don't need to be bombarded with a huge wallpaper or image.
Both ImageShack and Photobucket have these features built into their systems. Always choose the IMG clickable thumbnails for message boards - recommended on photobucket after you upload a new file or on Imageshack choose Hotlink for forums (1) option. Both will display a thumbnail and the thumbnail when clicked will open up the full size image.