This is an easy way to make a tackable surface. After my son has been taping or tacking stuff all over the walls I finally made this for him. The first thing I did was figure out the best place for it. I decided to put it between the door and dresser, a narrow space where he usually is taping pictures on the wall anyway.
I bought (2) 20" x 30" foam core boards, (micheal's 2.99 each) and I bought a piece of black flannel fabric, with a subtle herringbone pattern. I like having a dark background that isn't too busy so you're pictures pop out. Not shown, an exacto knife, ruler and I also bought some felt to do some cut-outs (optional), felt will easily adhere to the flannel so he can move the pieces around.
Foam core comes in different sizes, so figure out what size(s) are best for your space. You want to cut as little as possible, just easier. Butt the pieces together and use duct tape on both sides to attach them.
For mine, I taped the 2 pieces together making it now 20" x 60".
After I laid out my fabic, which is 54" wide, I realized I had to cut back the foam core a few inches so the fabric could wrap around. Its important to use a very sharp blade on your exacto knife & use a cutting board or a large piece of cardboard underneath because you will cut through. First I drew the line in pencil across. Before you cut, sheer the top layer of paper all the way across, along a ruler's edge. Then go back and cut all the way through.
I used duct tape to adhere the fabric to the foam core. I actually ran out so I used duct tape on 2 of the opposite sides and used a hot glue gun for the other 2, which worked great.
I used small 1" nails to attach it to the wall in the corners and along the side near the duct tape seam.
Using felt, which is super cheap and can make it custom for your child, I cut out a C for my son's name and Pikachu, from Pokémon, who he is obsessed with right now. I printed out a picture of Pikachu and traced it on the felt. He now wants me to add some more characters...I did the C free hand, it came out ok considering it was late, I did this at night while he was sleeping so he could wake up to it.