Forgo cleaners. Trying to remove stencils from your wall with a cleaner will not work. You will just be wasting your time and energy. A stencil pattern cannot be removed per se, and covering over it will likely cause the image to bleed through.
Sand it down. Using a piece of sandpaper, lightly sand down the pattern so it is flush with the wall. Make sure to sand down any bumps or texture. You want the wall to feel smooth when you run your hand over it.
Start with a blank canvas. Because stencil patterns cannot be washed away, the best thing to do is paint over them. Once you have sanded down the pattern, apply a coat of primer to the wall. Starting with primer will allow a better adhesive for the paint to stick to. It also helps eliminate any bleed-through that may occur. A second coat of primer may be needed for dark-color walls.
Let dry for at least 24 hours. This will ensure that the primer is completely dry before you begin the painting process.
Grab your brush. Once your wall is primed and dry you are ready to paint! Choose the same color as before or start fresh with a different color scheme.
Clean up. After your painting job is finished be sure to thoroughly clean and rinse your brushes. Allowing paint to dry on your brushes will cause them to become hard and useless.