If you are looking to customize your Windows Mobile device or your iPhone, you may want to head over to PortableThemes. The site has just launched but already features thousands of themes for Windows Mobile and Pocket PC devices and wallpapers for the iPhone and iPod touch.
If creating your own theme is more your thing, PortableThemes also features an online Theme Maker for Pocket PC and Windows Mobile devices. Find the image you want, pick the device type you want to make a theme for, then use our online theme maker with live preview to pick the colors scheme you want for the theme. Finally click Create Theme and PortableThemes.com will create the theme for you to download right away.
Best of all, the site is completely free and does not even require you to register to download themes and wallpapers.