What concepts of perception should designers be aware of when designing?
Not surprisingly, there's a huge load of stuff you need to consider when designing things for users. Here's a good paper written by some perception and vision researchers on the topic that might give you a more detailed introduction that what you have seen so far:

Healey, C.G. &amp; Enns, J.T. (in press). Attention and visual memory in visualization and computer graphics. IEEE Transactions on Visualization and Computer Graphics

It's open access as well!