GTK Theme with aplication

[José Maria Silveira Neto <silveiraneto gmail com>]

I saw very beautiful themes at art.gnome.org.
I'm making a game and this theme would fit very well:
http://art.gnome.org/images/thumbnails/gtk2/GTK2-MardiGrasDeux-Shot.png

I can tie and theme with an application? In such way that an user that
haven't the theme could see the app with the theme  (in KDE or GNOME)?

If there's a way, I would like to know.

Thanks.

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Silveira Neto