The Image Search API will only return a maximum of 64 results, in 8 "pages" of 8 results each. There is no known way to retrieve additional results via the Image Search API.
Furthermore, the Image Search API was deprecated in May 2011 and, per the deprecation policy, is due to be shut down in May. There is a chance that it may be allowed to operate beyond that, but I really would not count on it at this point in time.
I don't know what your application is, but you may want to consider the Custom Search API, which supports image search as well. You have to set up a Custom Search Engine (CSE) with image search enabled, and there are some strict limits on the number of free requests you can submit through the CSAPI, but you can retrieve up to 100 results.
jg