I guess you can apply this to many different things but mostly this is about web design. Its good to give you're users plenty of information but its bad when its overwhelming. This article talks about working on the flow of information and how it makes users feel. It mentions the kind of images you should use as well as layout and when its appropriate to have a challenging website vs a simple one.

http://www.boxesandarrows.com/view/design-for-emotion