Hi Carrier,
download smartgwt (excellent framework by the way) and look into this example:
file://localhost/Users/massimodipierro/Desktop/smartgwt-1.0b1/samples/Showcase/www/com.smartgwt.sample.showcase.Showcase/index.html#tiling_load_on_deamnd
which displays images in a tilegrid. The images are received from Yahoo via an http request. The response is in JSON. Look into the source code. To see the json response from Yahoo try the following URL:
http://api.search.yahoo.com/ImageSearchService/V1/imageSearch?appid=YahooDemo&output=json&query=snowboard
To make this work with web2py you need to replace that URL with the URL of a web2py action that returns a similar JSON response.
I do not know much about smartgwt but I am sure on the web2py google groups there are people willing to help.