You could check out other peoples work and see if it gets you inspired.

Can be any form of art and design, but personally i most often find myself inspired by modern or surreal art, or a broad variety of professional design and/or photography work... Also looking at galleries like the one on 'rosity can help.

Ofcourse you could also start doodling with pen and paper, and see if you run into any interesting ideas there.

Here's a few links i find inspiring:
http://www.behance.net   (Great variety of very interesting design and photography made by some very talented artists)
http://www.cgtalk.com   (A lot of very professional looking and sometimes really original 2d and 3d graphics)

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