DIY Vintage Window Frame Makeover

I started working on a fun and unique way to display our one-year anniversary cards, which I've written about before. I really wanted to frame them but that seemed a little bit too boring and predictable, and it was also proving to be difficult to find a large enough frame that was in my budget. 

I had remembered seeing a bunch of fantastic vintage windows in an antique shop nearby and suddenly I was feeling excited and inspired. The glass windowpanes are like mini frames, and I thought the vintage window would lend a cottage-y, whimsical look to the project. Here is the before picture of the window frame with the cards laid out on top (sorry it isn't great--I quickly snapped it with my iPhone and forgot to use my real camera). 

I decided to paint the frame a vintage gold (one of our wedding colors) to freshen it up. I also sprayed the hardware on top an oil-rubbed bronze. 

I love the way it turned out! However, I'm now at yet another impasse. I wanted to attach the notes to the back of the windowpanes so that they would, essentially, be framed and preserved under the glass. The problem is that I haven't yet found a way to do this. I bought glue dots, but they were very noticeable on the front of the cards. I bought a special glue online but when I tested it out, the dried glue was also quite visible. I thought about Mod Podge but I am afraid that they may cause our precious cards to wrinkle. I was hoping to go with a minimal approach to whatever adhesive I used and Mod Podge requires you to slather it on.

I'm still brainstorming but I'm not sure if I'll be able to solve this problem. I've actually been thinking lately that maybe it wasn't meant to be and that I should hang this window above my desk instead as a sort of bulletin board, attaching little post-its and notes to the panes (see the inspiration for this idea here). Sometimes you have to be flexible when it comes to DIY projects, adjusting your plans along the way. I do love this window and I put a fair amount of work into it, so I know it will be put to good use!