Why isn’t there a utility that would allow people to easily post a diagram? This is a chess forum, right?
I suppose someone could set up a position on a physical board, take a picture of it with a digital camera, then attach the image, but that seems like a lot of work.
One option is to quote a post that already has a diagram in it and then modify it.
If you do a quote on this post you will see that the board below is defined by a bunch of dashes and piece abbreviations. (copied from the thread viewtopic.php?f=23&t=16369 )
Big diagram:
[img]http://www.net-chess.com/diagram.cgi/rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR.jpg[/img]
Small diagram:
[img]http://www.net-chess.com/diagram.cgi/rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR/size.small/end.jpg[/img]