As a teacher, I have been very lucky. I've been in the same classroom since I started and have been allowed the ability to customize it and make it my own. My classroom looks MUCH different from when I first moved in.
One thing that I think might plague many teachers is not enough dry erase surfaces. Right now I'm facing the dilemma of removing one of my dry erase boards in favor of more shelves for books. I use every inch of my classroom. Vocabulary or important concepts are often written on the windows.
A couple years ago, desperate for more dry erase surfaces, I discovered dry erase paper rolls and turned one of my doors into a dry erase door. Several years later it still works great!
Step 1: BoM
Surface you want to turn into a dry erase board
Self adhesive dry erase paper (I used Go Write)
Glue sticks (upkeep)
Helper (extra hands always help)
Step 2: The Surface
The little cubby/office area in the first photo was/still is a useless spot. The first few years I was in my classroom it had no door. I came back from a break and found that our maintenance department built on a door for me. Because the doorway was so wide, they had to construct a doorframe that really didn't look good. I think looking at this ugly area in my otherwise very fun looking classroom is where I got the idea to put up something to cover it.
Step 3: Measure Twice
Measure out the strips of dry erase before you peel the paper protecting the adhesive backing. Measure twice, cut once. If you have a friend, have them help you remove the backing and line up your dry erase sheet evenly before pressing to your surface. I used a book to smooth out any wrinkles.
Repeat until your surface is covered.
Step 4: Upkeep
I have found that glue sticks work great for maintaining the dry erase sheets when the edges occasionally start to peel.
I use regular dry erase spray to clean the board. The dry erase paper has been up for at least 5 years now and is still working great!