Trouble creating a gallery style category

I need a gallery to list images as thumbnails. So I created a category and added these images (already uploaded to the NS web site hosting) as items. When I try to customize the template for the layout, I have troubles getting the urls of the images assigned to that category.
  On the image file page in NS, there is a list of all the urls belonging to that image. The attribute/tag name of the first url is "url" while the rest are unknown. I tried all codes such as:
  <img src="<%=getCurrentAttribute('item','storedisplayimage')%>">