The materials, estimated costs and half-ass directions below:

Materials:

Bookcase from Marketplace ($20)

4- 2x4x10's ($45)

2- 2x4x8's ($8)

2- 4'x8' smooth hardboard panels ($30)

4- 1x4x10 ($48)

6- 1x3x8 ($30)

3- 1x2x8 ($10)

Wood Screws ($8)

Accessible Beige Paint (already had, $0)

Caulk (already had, $0)

To start, I used the 2x4x10's to build a frame for the banquette seat.  It was roughly 9.5 feet long and 17" deep.  I assembled that in the garage, and when I had it all together, I brought it inside and mounted to the studs.  Once it was mounted, we carried in the bookcase and mounted that to the studs and the bench.  That's where the fun began.

Next, I moved onto the hardboard panels.  I planned out how to cut the two pieces of hardboard to cover the wall and the front of the banquette with all of the seams being covered with the board and batten trim pieces.  This is only the second project I've done where I completely planned every detail on graph paper before starting, and that saved me so much time while building.  This is a far cry from projects of the past and I highly recommend spending the time up front, rather than realizing a problem half-way through the project!  

From there I just added trim.  This is where is gets personal and you could add your own flare.  If I had chosen beadboard or shiplap panels, I could have just added a top and bottom piece of trim, caulked, painted and called it a day.  Ryan thought the board and batten would fit the style of our house better, so I used the 1x4's to trim out the tops and bottoms of the wall and bench paneling.  I used the 1x3's for all of the vertical pieces, including the outside edges of the bookcase.  Then I topped it all off with the 1x2's sitting horizontally.  

Fill, Caulk, Sand and Paint.  Voila!