Cheap or old fireplace screen. Be sure to buy the kind of fireplace screen that's made with glass, not mesh steel.

Rust Oleum spray paint in the color of your choice. I like to use the frosted glass Rust Oleum spray.

Paint the glass back of the fireplace screen with Rust Oleum paint. If you're going to use frosted glass (which is my favorite) don't make the frosting too thick. This way, the color of your wall will still show through the frosted wall art once it's hung

For more ideas on creating your own wall art, please read my article about 10 wall decor ideas you can make yourself.