Under some topics here like this one there's the "Attachments and other options" available below the typing box. You can attach several file types, including pictures.
If you want an attached pic to show in your post, there's a trick: After posting read your post and right click the attachment. Choose "Copy link location". Then modify your post, click the "Insert image" farthest left in the tool bar and paste the link location between the bracketed [img]http://commands. Save and the image is in your post for all to see.
Somehow I can't make it work now.