If you buy one then dont like yours can you re-do it without pay?
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or anyway to preview it?

yes

Try to be more specific. ~Solax

You can always upload a new texture if you please.

Usually if you want to veiw a texture there are methods (in gimp/ps) to make the flat texture into a sphere and test it out. The best way for me is just to upload it and check it out ingame.

If you are buying a head then the artist usually provides a spiny .gif to show you how it may look.