I documented my process a little since it took me a few weekends to complete, so I'll go through it for you. Everything I used can be purchased at your local craft store. The box I used had hinges and a latch which I took off before painting. I put the hinges back on later, but left out the latch.
First I started out by painting the whole thing in dark blue. Then I dry brushed over that with light blue, white, and aqua, that I diluted with a little water. That's what gave it the weathered and multi-colored look. I liked the way that turned out because it really showed off the wood grain. I used acrylic craft paint and I made all the colors myself with only a bottle of blue, red, yellow, and white.
For the letters I took scrap booking letter stickers, (the kind that don't have white space around them) and placed them on the edge. Then I painted the edge with about 3 or 4 coats of white. After it dried I peeled off the stickers with a knife and ta-da! Perfect letters!
I also added the date on the back. The paint did bleed a little under the stickers, but I thought that added to the rustic look of it.
Then I painted the flowers on. I used a computer print out and some white carbon paper to trace an outline on the box and then I painted it in with some very small angled brushes.
I did the flowers on top the same way, and I also painted a border to extend the white a little onto the top because the white edges bled a little.
I also painted the entire inside of the box white, and added ribbons to keep it from opening all the way and tipping over. (I'll add some pictures of that when I get a chance)
So there it is! I'm very pleased with it! I loved doing this too. I might even make a few more in the future if I ever feel inspired again! Maybe for a friends wedding or something! It also serves a purpose after the wedding too because its so personalized. We are using it to keep all our keepsakes from the wedding, like my garter and the cork from the champagne. I guess its like a "memory" box now. We can open it up later and remember our day together :D