Unfortunately, wall decal is not designed to be reused. Once you remove the decal, it is not reusable as the vinyl material will stretch out of shape and the adhesive will be weaken as well.
However, in some circumstances, wall decal may be reused. Simple designs such as polka dots, stars, rings, etc can be carefully removed from your surface and reapplied to another surface. However, due to the nature of the material as well as variances in ways people tend to attempt to remove their decal, we cannot guarantee that every design can be reused.