Sure thing -- There's a button on the "post reply" form that has a little tree on it. (  ).  Click there, and up will pop a box asking for the URL of the image you want to display.  Enter the URL to the image, and click the "OK" button.
 
This requires that you have the image you want to add to the page somewhere on the internet -- I use my personal web space at my ISP, but there are photo sharing sites out there or free web space providers that you could use as well.    Just save your doodle in a web-compatible format (gif, jpg, png), upload it to your web space, and then use the "Add Image" button there to include it in a post.