Just finished version 1 of my first iGoogle theme. I must say, google made it very easy. I think everybody can do this who has some photoshop and XML knowledge.
This is a screenshot of the theme:
This screen changes 3 times a day, here the other skins:
Next the xml file that I used for this theme:
<?xml version="1.0" encoding="UTF-8" ?>
<ConfigMaps>
<ConfigMap type="Skin">
<Meta name="title">Jotunheimen</Meta>
<Meta name="description">Theme about the Giants of Norway</Meta>
<Meta name="author">mark deraeve</Meta>
<Meta name="author_email">mark.deraeve@gmail.com</Meta>
<Meta name="thumbnail">http://www.dailycode.net/iGoogle/thumb.jpg</Meta>
<Meta name="screenshot">http://www.dailycode.net/iGoogle/screen.jpg</Meta>
</ConfigMap>
<ConfigMap type="Skin">
<Trait name="TimeOfDay">12am-8am</Trait>
<Attribute name="header.background_color">#FFFFFF</Attribute>
<Attribute name="header.tile_image.url">http://www.dailycode.net/iGoogle/header1.jpg</Attribute>
<Attribute name="header.logo">white</Attribute>
<Attribute name="header.link_color">#3366CC</Attribute>
<Attribute name="header.text_color">#3366CC</Attribute>
<Attribute name="navbar.border_color">#3366CC</Attribute>
<Attribute name="gadget_area.gadget.header.background_color">#AEC3E2</Attribute>
<Attribute name="footer.background_color">#FFFFFF</Attribute>
<Attribute name="footer.center_image.url">http://www.dailycode.net/iGoogle/footer1.jpg</Attribute>
<Attribute name="footer.link_color">#3366CC</Attribute>
<Attribute name="footer.text_color">#3366CC</Attribute>
</ConfigMap>
<ConfigMap type="Skin">
<Trait name="TimeOfDay">8am-12pm</Trait>
<Trait name="TimeOfDay">8pm-12am</Trait>
<Attribute name="header.background_color">#FFFFFF</Attribute>
<Attribute name="header.tile_image.url">http://www.dailycode.net/iGoogle/header2.jpg</Attribute>
<Attribute name="header.logo">white</Attribute>
<Attribute name="header.link_color">#FFFFFF</Attribute>
<Attribute name="header.text_color">#FFFFFF</Attribute>
<Attribute name="gadget_area.gadget.header.background_color">#AEC3E2</Attribute>
<Attribute name="footer.background_color">#FFFFFF</Attribute>
<Attribute name="footer.center_image.url">http://www.dailycode.net/iGoogle/footer2.jpg</Attribute>
<Attribute name="footer.link_color">#3366CC</Attribute>
<Attribute name="footer.text_color">#3366CC</Attribute>
</ConfigMap>
<ConfigMap type="Skin">
<Trait name="TimeOfDay">12pm-8pm</Trait>
<Attribute name="header.background_color">#7F0000</Attribute>
<Attribute name="header.tile_image.url">http://www.dailycode.net/iGoogle/header3.jpg</Attribute>
<Attribute name="header.logo">white</Attribute>
<Attribute name="header.link_color">#7F0000</Attribute>
<Attribute name="header.text_color">#7F0000</Attribute>
<Attribute name="gadget_area.gadget.header.background_color">#AEC3E2</Attribute>
<Attribute name="footer.background_color">#7F0000</Attribute>
<Attribute name="footer.center_image.url">http://www.dailycode.net/iGoogle/footer3.jpg</Attribute>
<Attribute name="footer.link_color">#3366CC</Attribute>
<Attribute name="footer.text_color">#3366CC</Attribute>
</ConfigMap>
</ConfigMaps>
If you want to test your theme, there are several developers gadgets, but the most simple way is to use the querystring provided by google. For example: http://www.google.com/ig?skin=http://www.dailycode.net/iGoogle/JOtunheimen.xml . You will have to put the xml file along with all used pictures somewhere on a internet server. Then just point out to the xml file.
That's all there is to it!