David,
Generally you'd put the images under the generic www directory. On OpenACS 5 there is a /resources directory, but I believe you are using OpenACS 4.6.3.
To link image into an ETP page, you need to enter the HTML for the img tag. ETP doesn't have any way to attach images along with a etp page.
I have been thinking of various ways to do this. One way would be to define a template that had "holes" in it for images, and allow the user to select the number of images to fill in these spaces.
What sort of images are you trying to add to the pages? That is, what are they for? For OpenACS.org, for example, all the graphics are in the templates that style the pages. Generally the content is just text.
