An object that can be evaluated or interpreted differently by different subjects observing it.
An example is the series of portraits done by Guim Tió, where black and white portraits receive strokes of colored paint. The meaning of the added color is abstract and open to interpretation.
http://www.guimtio.com/no-name-project-2/
This is commonly seen in the world of matte paintings, where realistic artwork is used as backdrops in film, often imitating large spaces that are too expensive to build a set for. Mathieu Raynault has a studio for producing this kind of work.
http://www.raynault.com/galleries
This can be used in the work of Rob Gonsalves, who uses optical illusions to combine realistic scenes in unrealistic ways.
https://www.facebook.com/RobGonsalves.Official/
Chris Maynard carves images from feathers, a strong symbol for flight and freedom.
Murray Fredericks uses a mirror to juxtapose two different views of a lake.
http://www.hamiltonsgallery.com/exhibitions/113/works/
Yaacov Agam uses repetition in shape and color to build optical effects and illusions.