Right now, you're correct that you can't add an image by attaching it.
However, if you upload it to a site like Picasa, Google Pages, Snapfish, or a host of other online storage places, you can insert the image easily. There are two ways I understand you can do it. I use the first, but many others use the second with great success.
First, upload the image to whatever site you want to host it. Click on the picture and write down the URL for where that particular photo is stored.
Then here's the two methods for inserting it here:
1. In the body of your message, type [ img ] then paste the URL then type [ / img ] (no spaces in between the brakets).
2. In the body of your message type <img src="[paste URL here]"> (Jason Meadors also explains it quite well in this post: http://ncraonline.org/forum/forums/p/1734/3149.aspx#3149)
So here's an example of an image I uploaded to my Picasa album taken at the convention in Dallas:
<img src="http://lh3.google.com/candisbradshaw/RsCiT0u7i8I/AAAAAAAABGo/L0X97gG08eg/DSC00614.JPG?imgmax=912">
Hope this helps!

Perseverance is not a long race; it is many short races one after another.
- Walter Elliott