The call to theme.init() accepts a range of different options, described below:

Key Usage Default value
hitName Name of the items to search, used in the XXX items found item
placeholder Text displayed in the searchbar when query is empty Search for anything
transforms Transforms to apply to each hit {}
widgets Array of additional InstantSearch widgets to add to the page []

Also have a look at the Algolia frontend helper to lazyload your search result images.