To place an image in a page or a post you’ll need to know it’s URL. Most client are going to be confused when they clink on the image icon to insert an image and they don’t see a upload or browse option.
Pixie does have a nice file manager that you can upload images and files into, but it’s not without problems. For example, if you upload an image that has a file name with a space it will not except the image. It’ll tell you there is a bad character, but it doesn’t tell you how to fix it. For a beginner this would be confusing.
To get around this you could train the user to first upload any images they plan on using into the file manager and then to copy the url by right-clicking the view link and the choosing copy url. Then paste these url you want into a text editor so when your writing your post you can just paste the URL from your notes. Or maybe you’ll get lucky and find out the end user uses Flickr, Picassa, MobileMe or some other photo sharing services to post their images online. If this is the case it will be easy to show them how to get the URL and then use it place an image.