Many forums have the option to have images thumbnailed by default. This can help to save bandwidth for users with poor internet connections, and some users (me) prefer to have small previews of images that can be expanded on command, rather than huge images directly in the body of the post. Especially in cases of large screenshots these directly embedded images don't look great and will eat up user's data caps.
Add the capability to have images be rendered as thumbnails that can then be expanded into full sized images. I'm not sure if this should be an option for the poster (i.e. toggle on the thumbnail setting when posting) or the viewer (render all images as thumbnails by default). Images should either open in a simple viewer window overlay (as in something like XenForo) or simply expand to their full size (like on an imageboard).
