Thank you all for your replies.
Andrew when I change the imageMso="Lunge" to image="Lunge" it doesn't change the gallery icon. It remains as an autotext icon.

If I change it to gallery id (instead of idMso) and image ="Lunge" then the icon changes but then I loose the ability to access the gallery (auto text).

Any suggestions, or is it the fact that gallery icons can only be change to built-in icons and not custom ones?