"I'd like to capture an image into a form, and then show that image on other pages of the form..."

This can be accomplished by creating an AfterSetData event handler to the source (capturing) Image Annotation field. Then, set the AttachmentID property of the target Image Annotation field(s) to the AttachmentID of the source Image Annotation field. Your VB .NET form script will look something like this:

    <MiCode(ControlScriptEventType.AfterSetData, "ImageAnnotation")> _

    Public Sub Ctl_ImageAnnotation_AfterSetData(ByVal e As AfterSetDataEventArgs)

        _ImageAnnotation_2.AttachmentID = _ImageAnnotation.AttachmentID

    End Sub

If there are multiple Image Annotation fields, simply set their AttachmentID property as well.

All Image Annotation fields with the same AttachmentID will be referencing the same image attachment in the form.

See the attached form for an example.