I actually used a florist envelope as a template--I dismantled it, then traced it, then used Zots to glue the new ones together. They were held into the guest book with a normal glue stick. People wrote on the cards that are in a little stack above the book, then they tucked them into the envelopes. I lucked out, because one of my brothers actually worked in a paper factory at the time, but it was closing down, so the staff was allowed to take all the paper they wanted. I literally have a case of packages of different card stock and scrapbooking paper in my basement!
I know, the brown was actually a late addition. Over the course of my two-year engagement, it was originally just the blue and white (I knew I wanted blue, because I am a blue-stone bride), until about a year before the wedding. I added the brown because I needed a little more wiggle room when choosing wedding elements. I actually ended up loving that combo way more!