Blu tack handy pack.
Blu Tack is a clean, safe, easy-to-use reusable adhesive commonly used to attach lightweight objects to walls, but also useful in model making for holding parts during constuction of model buildings, on theatre design models & on stop-motion animation sets.
Do not use on porous surfaces (eg non-vinyl wallpapers) as staining may occur.
Strengths increases with age so take care when removing.