I did a movie theme last year and it was so much fun. Here are some of the things I did...
I got black fabric and hung it around my large blackboard like a big movie curtain. I just gathered and stapled it across the top and hung it down the sides. It really was a focal point and made it look just like a real movie theater.
For one of my bulletin boards I got some red and white striped fabric and cut it into the shape of a popcorn bag. Then I bunched up yellow and white paper and stapled it like it was spilling out of the bag and I wrote... "Great work is popping up!"
You could use plastic popcorn holders for supplies, a red carpet area,
Here are some other bulletin boards slogans you could use...
"Now starring in 3rd grade ..."
"Books in Review"
"_________"s in the spotlight"
"Places Everyone.... "was one title I used for a place value unit at the beginning of the year
Hope these help