Update: There is a pattern available for this now: the Flora Needle Book pattern, available for instant download at Etsy and Craftsy.
I thought I'd be smart and sew in little ridges to slip the needles through. They are staggered so it doesn't make a hump in the book. I'm not sure if it is worth the extra effort. I also thought about sewing in a little tuck in the pages to do the same thing, but didn't want it to run the entire length of the page and make it lumpy in the spine.
I also need a needle cushion. I often stick needles in my pin cushion while I'm working and this is not a good idea, because:
1) I somehow always manage to push them down inside.
2) I forget they are lurking in there and they skewer my finger when I squeeze the cushion in the wrong place.
I need to make a shallow cushion with something to stop the needles poking through in the bottom. Maybe an egg cup would make a good start. I have one I thrifted a while back.
In any case, I'm so glad I don't have to store my needles like this anymore: