I bought a wooden "C" for my daughter years ago and have finally got around to doing something with it for her bedroom door! Her fave colour is blue at present, so I chose some co-ordinating papers from my stash. It was super easy to do. I just painted the edges brown, then once dry, painted on PVA to stick the papers to. To get the papers the right size, you just place the letter over the top and trace around the outside. I tore roughly the places I wanted the papers to meet together, to make it look more home-made and vintage. I also used brown ink on a sponge to dab around the edges of the papers to get an aged look. Once stuck down, I painted (thinly) PVA glue over the top of the whole thing, to seal it. I got a triangle template online and used it to cut the bunting pieces and stuck on sticky letters for her name and attached them at the back to some embroidery thread with sellotape. In hindsight, I wish I'd used a template where you fold over the back and glue down, it would last longer. I used PVA to glue it down and attached some black rhinestones over the bows. I wish I'd had a good stamp for the black swirly bit over the blue and white spotty paper, but I used a stick on instead. I wrote some lovely things about my daughter on a tag and attached.
She just loves it. I attached to the door with those velcro removable 3M thingies, it makes it sit flatter and will hopefully stand up to those door slamming years! ;-)