What you will need
An old set of cork backed placemats
Glue (I used self adhesive photo paper and did not need the glue)
Spray or brush on varnish or lacquer (I used the spray on variety as that was what I already had)
Step 1: Sand the Old Varnish and Wet
You could use the sandpaper to remove the old image but I did not bother to go that far, I just removed the existing varnish.
Once the varnish is removed then I quickly placed the placemat under running water and then set it aside while I sanded the next placemat. I DID NOT soak the placemat or place a wet cloth over the top of the placemat as I only wanted to cause the image to lift off and did not want to risk causing the placemat itself to warp from getting too wet.
Step 2: Remove the Old Image
The time it took to peel off the image varied from placemat to placemat depending on how well I had sanded them. The quickest was about 10 minutes to remove the whole image while the toughest one (which I hadn't sanded as well as the others as I was getting bored) probably took me 40 minutes. Sighhhhh, I should have spent the extra time sanding.
Step 3: Apply a New Image
Remember to select your paper as "landscape" or your image will be shown the wrong way on the placemat.
Stick paper onto old placemat either with glue or using its own self adhesive covering.
The image on the original placemats had finished a little inside the edge of the wood. I figured this was so that the varnish would cover the edges of the photographic paper and waterproof your image. I used a scalpel and metal ruler to give me a neat edge once the paper had been applied to the wood. Hmmm, note to self, don't try and do this freehand as you end up with a wobbly edge.
Step 4: Varnish
Allow time for the varnish to dry and enjoy your lovely new placemats.