I have the forum configuration set to not display attached images. I did this in the interests of folks on slow connections, so they have the choice of downloading the attachment or not, but still get to read the message.
If you really must include an image in a message, I suggest it be a small one and, if you want folks to see a larger one, make the small image a link to the larger one.
If you're inserting an image with no link:
If you're inserting an image as a link:
Replace my curly brackets with square ones. Here's how the latter would look to the reader:
If you use the insert image
tool, it merely inserts the
tags, and you need to put the address of the image between them.