You can do the same in blog posts as I use to display the whole image in a forum thread - upload the image as an attachment and then use the attachment ID in an IMG tag. For example (replace the <> characters with square brackets):
<IMG>https://www.fantasygrounds.com/forums/attachment.php?attachmentid=XXXXX</IMG>
Where XXXXX is the attachment ID - you can get this by briefly adding the attachment (once uploaded) to your post.