We would really like to see some new themes created for Invision. If you would like to create complete themes for Invision, please do so and then provide the link(s) here. We'll be happy to host the themes along with the author's name.
Themes should be complete and not just include a different toolbar image or switchbar image. All images should be changed for the theme. To get an idea of what can be changed, look into the Theme Manager. You can choose to only change the graphical theme, or you can also change the sound theme.