Decorating and Design - wall decoration

My daughter wants to cover styrofoam boards (5/8 - 1") with fabric and put them on her walls. They will be about 2' x 2-4'. The idea is just add a splash of colour but I'm sure she will use them to display photos and posters.
How can I attach them to the walls without leaving a mess when they are removed? One of them will be low on the wall so there is always a chance it could be bumped/touched, so they need to be pretty secure.
Thanks for any help.

i would just screw them to the wall in each corner, and depending on how heavy they are, using wall anchors. they're easy enough to pull out later & you can always spackle the holes they leave. then use something decorative to cover the screw heads, like flower patches or cute buttons or whatever - you can just hot glue something over them.

Thanks, Annette, I will try that. They actually have very little weight to them.
I would have thought styrofoam was too fragile to attach with screws, that it might break off. I guess I should just make sure the screws are placed a couple inches in from each side.