I would like to allow the user to select one of several pre-supplied images. Is there a standard way to do this?
The only thing similar to this that is Standard would be the Image Picker control. However for this to work you would have to add your images to the iPhone's image library and the user would have to pick them from out of all their other pictures.
What you need to do is build something similar.
You can go as easy or complex as you need/want.
I would go simple (as that is the idea of the iPhone) and have a scroll view (depending on the number of pictures you want) and load thumbnails of the images. When they select one, you do something with it. (Look at the view when you are looking in a photo album on the iphone)
I believe I have seen open-source representations of this before. I would check google code.
I use a UITableView for this, with a thumbnail and description of the image they're choosing.