I finally made one of these signs that are all over Pinterest.
Start with a painted canvas; I found this one at Goodwill for $1.99 and worth every penny.
I wiped on acrylic metallic peridot paint over some of the white spaces to add some more color.
The hardest part is deciding on what words will work for the size of your canvas. Since mine is going down in the newly upgraded family room, I wanted a beach theme and fiddled around until I found words that would fit. I got the two inch repositionable vinyl letters at Staples.
Run your fingers around the letters to make sure there are no air bubbles and that all the edges are stuck down on the canvas.
I painted my canvas dark blue - it took 3 coats to cover the painting and even then I had to go over some spots after removing the letters. You can see some of the spots that need more paint.
It's a bit tricky to get the letters off without gouging up the paint. It worked best to press a fingernail firmly into the corner of a letter and pull it a bit to start lifting off the letter. I did get a few spots where the blue paint ooched under the letter, but the paint was easy to flick off with a craft knife.
After a few touch-ups with the dark paint my sign is ready to hang.
This is a bit like magic - you're never quite sure what's going to show up under the letters. I bet this technique could even save those 50s paint-by-numbers from eternal humiliation.