Use stencils to write something inspirational on the wall.
Make use of flowers and branches to make some art.
Use decals to make some nice art work on the wall.
Wood can be made into really interesting art for the wall art.
Generally throw on some paint to make freestyle art.
Make a collage of interesting pictures.
Use black and white pictures in an interesting manner.
Make shelves in interesting patterns.
Use colorful dots in an interesting way to make wall art.
Put together mirrors in an artistic way.
Use colored tiles to create a cute pattern.