The HTML editor is based on the open source editor FCKeditor. A few features have been removed, because they would require some server side code. One of them is to include images into the entered text.
The last edition contained a very interesting tip which shows how to re-enable the “Add picture” feature for the FCKeditor.
The article is only available in german, but with the help of Google Translation you should get enough information to follow the step by step instruction.
For the translated version you have to scroll to the right to see the images. I don’t know why Google Translate is doing that.
BTW, if you haven’t subscribed yet to the biweekly editions of the German APEX Community, you should do now!