The following tutorial covers logo replacement in SkyCream diazo theme on a Plone 4.2 website.
Diazo SkyCreamo Plone Theme uses default Plone 4 logotype:
You can replace this logo with yours via ZMI. Open portal_skins -> sunburst_images folder, there is logo.png image. To set your own logo press Customize button:
Press Browse button to select your own logo. Click Upload:
Now you have a new logo.png image, and it is automatically put into custom folder. We recommend using transparent images in .png format (that use alpha-channel) as SkyCream theme logo. This allows using images containing pixels with different level of transparency that will suit perfectly to the theme. Since we use such transparent images as example logo image - it is not visible on a white background.
Now when you return to Plone interface, you'll see a logo image.
For the subsequent logo replacements go directly to ZMI portal_skins/custom/logo.png and upload new logo image there.