I think I’ve come across a minor bug. I’ve followed these instrctions to add an image field to a custom taxonomy page which works fine. However, I’ve noticed after I add a new term the in the image field on the page disappears. If I refresh the page the image field will then reappear.
I think it has something to do with the way the form on the category list page reloads through AJAX. I think this is a new feature on this page in WP. To be honest, I dislike the fields appearing here and I wish that WP would make the add work like the posts, opening the term edit page instead of having it directly on the list page, but that would only be useful for us people that highly customize the taxonomy/terms editor.