I use book shelves to store my fabric too. To cover the fabric to protect from dust and fading, I put a tension rod inside the bookcase at the top and made a curtain panel with cafe curtain rings on the top edge. The rings let the panel slide to either side, out of the way, when I want to see the fabric.
Since your storage units extend beyond the front of the shelves, maybe DH could mount a curtain rod that would extend out 3 - 5 inches, and your panel could slide on that. Not as good as doors, but effective! I made my panels out of some $1.00 per yard fabric from Walmart's bargain table. It was bright and pretty and I bought all they had (about 19 yds) knowing that I would use it somewhere. Looks good.
Your room is great ... lots of planning went into that!