If I select a field type as Joomla user, it should show a combo list in the form layout, but instead of showing combo list, it is just showing a text field.

Similarly, If I select a field type as Access, it should also show a combo list in form layout, but it is also showing a text field.

I have tried using joomla 3.2, 2.5, 1.7 all are giving the same result in the sand box.

Am I missing something or is it a bug?

This is happening in both Backend and Frontend layouts.

Trying to upload a Jpeg here to show the problem, but this forum is not allowing me to upload a jpeg or png file

This is a classic one.

In the fields tree, open the node of your FK and take the sub-field to show as label.

That's it.