Backbone subviews with non-uniform layout
This looks pretty good. My main suggestion for improvement would be we how you set and create the columns. I would try and make this more dynamic so the amount of columns can more easily change, and can be set from code using this view. 

To do this I'd create an array to represent the columns. Each column would have information about whether its narrow, or wide and then how many items it should have in it:

columns = [{type: 'narrow', itemsPer: 3}, {type: 'wide', itemsPer: 2}, 
  {type: 'narrow', itemsPer: 3}]


And then process the array rather then have variables named for each column. This would also add the items to the columns so it can be done it one loop. I used "shift" to remove the first element of the array so the narrow collection could be used without referencing exact indexes, which would allow it to work for any amount of items per column. I also changed the structure of the narrow and wide variables so they are properties on a items object, which makes the referenced with the same column.type name. 

items[narrow] = @collection.where display: 'narrow'
items[wide] = @collection.where display: 'wide' 

if narrow.length &gt;= 6 and wide.length &gt;= 2
  for column in columns    
    columnHtml = $(@template).addClass('column-' + column.type)
    for i in range(column.itemsPer)
      @addOne(items[column.type].shift(), columnHtml)

    @$el.append(columnHtml)


Another thing, I found the template property to be confusing, because it was the template for each of the three columns where I expected it to be the template for the whole view (which would only be created once). I suggest naming it to something like "columnTemplate" 

columnTemplate: '&lt;div class="column"&gt;&lt;/div&gt;',


My code examples are in pseudo code, as I'm less familiar with CoffeeScript, but I think you can understand generally what I'm saying.