I just learned a little tip and thought I would pass it along. I discovered this as a result of doing morning pages for The Artist's Way course. The first thing I discovered is how helpful it is to write everything down. It clears the mind of the small things and opens it up to creative ideas. I figured if it works for that it would work for designing also...
If you know the subject you want to work with, but are stuck for ideas, write it down and just brainstorm. Here's my example: Alaska-I thought of glaciers, mountains, salmon, bears, eagles, totem poles, button robes--there were many more, but you get the idea! Somewhere in there, I know is a creative idea. You can further break this idea down--say you want to work with glaciers: cold, massive, the deep aqua blue of the ice being so dense, the cracking sound they make when huge chunks calf off.
You can apply this same thing to materials. For example, think, "What can I do with feathers?" Trust me, the ideas will flow out. The more you do this, the better it seems to work.
All these ideas will train your mind to "wander" onto something the previous thing made you think of. I can't stress enough how helpful it is to write these ramblings down! I hope I've explained this clearly!