You can upload images wherever you like, the same in the newsletter editor as other editors, click the image toolbar item and from the dialog click the button to browse the server, from there you can browse images or upload new ones, then select one and it will go into the editor.
Unfortunately html for email is very challenging to get decent designs that work in popular email clients, much more difficult than styling for the web browser. You can get a number of decent free html email templates here:
http://www.campaignmonitor.com/templates/
Those are far better than the few we include in mojoPortal. You would have to paste in the html using the source view of the editor.
Hope it helps,
Joe