Who do the fields belong to, the VIEWING User or the Item Author? Data (to include user fields) for the Viewing User are available in all templates, so you could edit the template and include the specific field(s) in the location you want. If its the Showcase Item Author's fields, I don't think that data is available (and if it is, its probably not prepared). The later would require additional programming code.
Once again, I should have taken more time to explain...sorry for being so imprecise.
Let me try to be more precise :
When you register at my forum, you have to fill the usual fields and some custom fields, as shown below:
In the above picture, I've highlighted the one I'm interested by. It's called "Field_editmypicture".
Let say you register to my forum: you'll fill this field. Then you decide to create an item in the showcase section.
Is it possible is to show somewhere in the item you've created your value of this field "Field_editmypicture"?