http://www.dakkadakka.com/dakkaforum/posts/list/31.page JForum - http://www.jforum.net
Khorne is obviously a skull, Slannesh is a combination of the male and female symbols and Nurgle looks like it's based on the biohazard symbol, all of which make sense.

But Tzeentch is a sort of Flame-y thing. Is it meant to be a flame? A very badly broken oroborous (which would make some sense) or what?]]> http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5710139.page http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5710139.page GMT
It is the serpent, by whose words great change is begun, for he is the Changer of the Ways.

It is a tongue of flame, as evidenced by his daemons, and the fires of the warp bring mutation as well as destruction, for he is the Great Mutator.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5711209.page http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5711209.page GMT ]]> http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5711896.page http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5711896.page GMT http://wh40k.lexicanum.com/mediawiki/images/thumb/7/73/Tzeentch_mark.png/160px-Tzeentch_mark.png

The latter is in actuality a swimming fish I believe, its certainly been depicted as such in Fantasy books. Makes sense, ever moving, ever changing..
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It could represent any number of things all at the same time.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5712431.page http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5712431.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5713841.page http://www.dakkadakka.com/dakkaforum/posts/preList/532007/5713841.page GMT