UX suggestion: example search already performed on the landing page. You can fake it a bit so it's not actually hitting your search logic (and incurring that cost) every time. Just so when you arrive you see the sort of thing a search might return.

[EDIT] Actually instead of dropping straight into the actual search-result UI, how about scrunching the header up a tad more (there's already a bunch of incomplete-looking space under it) and a row of example images with example searches that might bring them up:

    [ Image ]       [ Image ]      [ Image ]
    "Cats playing    "The moon,    "Statue of
     baseball"        made of       liberty
                      cheese"       driving a car"