Can I use Styrofoam ceiling tiles on my wall?

Yes, you can install them on your wall but I would not recommend installing them in an area that will most likely get touched, kicked or it is a high traffic area.  The reason is that the tiles are soft and can get damaged when kicked or hit, even with your nails they can be damaged.  So, it can work but but they may get damaged.  They should be fine as a wall art, few feet from the ground or on a wall where there is no traffic.  Lot of Photographers use them for backgrounds.