I want to use graphics from a website like the KI Teacher's lounge in a mailing

As long as a graphic is reasonably sized, and available on the web for you to link to, you can include it in a mailing or a template using an HTML image tag. 

Go to the image or pdf file you want to include and right click (Mac CTRL Click) it to COPY a LINK to it.

In the YourVirtuoso Content editor for the mailing or template, paste this link inside an IMG tag like this:

<IMG src="paste the link here">

You should end up with something like:

<IMG src="http://www.kindermusik.com/new/images/7_2007_enotes_Images/DemoDaysPostcard.pdf">

If you put align="center" between the IMG and the src= it will center the image in your email. You can try right and left too if you want. After that it's up to you and your HTML reference book! 

One more thing, Kindermusik may not keep these images on the website forever, so it is up to you to check from time to time to be sure they still work. At least the YourVirtuoso editor gives you a preview, so you will see when you create the email if it is working...