This old medicine cabinet has been reused as a hidden wall compartment. Apartment Therapy recommends finding these at local reuse stores. Set it into the wall, and attache a large picture frame in place of the original...
This Danish company makes drawers that fit into stairs. Without a translator, I’m not sure if they are a kit or custom installs, but either way it’s a solution to a common storage problem; what do you do with that little bit of space underneath the bottom...
This bed frame from IKEA allows the mattress to pivot up and reveal a secret storage area underneath. It makes good use of wasted space, but this concept could be used to custom build a much stronger secure area below your bed. Or I guess you could just get a Bed...