Just because you live in a rented space where you aren't allowed to nail stuff into the wall does not mean that your walls have to be completely bare for the rest of your rental agreement.
Adhesive strips and adhesive hooks are your best friend, the latter which can be used to hang fabric shower curtains over your windows. You can also add a quick splash of patterned color with removable wall paper, wall decals, or create your own geometric patterns and shapes with washi tape.
Read below for more ideas on adding no-nail wall art to your home. Click on image to enlarge.