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http://www.pixentral.com/show.php?picture=1jPPvboSFJnSdU3q7b RI5ccTCeWZo0>
Take a look at this. (I did it in Illy but you can do it in Photoshop pretty much as easily.
Make some random coloured shapes set to multiply or a photographic image. Mask with an equilateral triangle. Reflect/copy this and rotate by 30°. Move the corners so that they touch. Link/Group and Rotate/Copy by 120°. And again. Get all the corners to line up and bingo.