Transparent Images & Backgrounds
Google Docs are fantastic, but one of the few things they are missing is a tool like Instant Alpha, that will allow you to delete the background of an image, effectively creating a transparent background.
Well there are two ways around this:
Search for transparent images
When you search for an image, use Google's search tools to restrict the images to those with transparent backgrounds. Search for an image, open Tools, then choose Transparent from the drop down menu.
Sometimes the perfect image is not transparent, but does have a plain (usually white) background, you can download it, and edit to make it transparent. Open the image with a plain background in Preview and use the Instant Alpha tool to select and delete the background, making it transparent, Preview will automatically prompt you to save as a png file (images have to be png to support transparency), and you're good to go.