Para adquirir o link da imagem o melhor é escolher a imagem no picasa web albuns e copiar o link para a imagem (não é o link do site) no botão fornecido. Os tamanhos disponiveis são os seguintes:

The following values are valid for the thumbsize and imgmax query parameters and are embeddable on a webpage. These images are available as both cropped(c) and uncropped(u) sizes by appending c or u to the size. As an example, to retrieve a 72 pixel image that is cropped, you would specify 72c, while to retrieve the uncropped image, you would specify 72u for the thumbsize or imgmax query parameter values.

32, 48, 64, 72, 144, 160

The following values are valid for the thumbsize and imgmax query parameters and are embeddable on a webpage. These images are available as only uncropped(u) sizes by appending u to the size or just passing the size value without appending anything.

200, 288, 320, 400, 512, 576, 640, 720, 800

The following values are valid for the thumbsize and imgmax query parameters and are not embeddable on a webpage. These image sizes are only available in uncropped format and are accessed using only the size (no u is appended to the size).

912, 1024, 1152, 1280, 1440, 1600

Este exemplo tem o thumbnail cortado

http://lh4.ggpht.com/_luuhjfFnfV8/SeOEK7_pk2I/AAAAAAAAAi0/fUXCfz9NSxU/s160-c/17.JPG

O texto a vermelho indica o tamanho da imagem e se deve ser cortada ou não

Este exemplo tem o thumbnail normal

http://lh4.ggpht.com/_luuhjfFnfV8/SeOEK7_pk2I/AAAAAAAAAi0/fUXCfz9NSxU/s160/17.JPG