Inexpensive craft store frames fit perfectly around light switch covers! --I like the LOOK Expensive (but not really BE expensive! -- 31 Easy DIY Upgrades That Will Make Your Home Look More Expensive--
Another pinner exclaimed: 28 Decorating Tricks To Brighten Up Your Rented Home (or college apartments) - I especially like the washi tape picture frames and the DIY photo wall. Nice DIY home decor list.