Google may get three times more search traffic than Yahoo, but, SearchWiki aside, most of the innovation seems to be coming from Yahoo and Microsoft’s Live Search as they strive to gain a larger slice of the search market share.

Last year Yahoo introduced Search Assist, an advanced autocomplete feature that recommends related searches as you type your query into the search box. Autocomplete isn’t a new concept – Google has offered it for years through Firefox and its browser toolbar (and recently integrated it into its homepage). But Yahoo takes it a step further, going beyond just guessing what word you’re typing by suggesting possible related searches.

Today the site is introducing thumbnail previews for its image searches, allowing users to see how they should modify their queries to get the set of images they’re looking for. For example, typing “Obama” presents suggested searches for “Obama family”, “Barack Obama”, and “Michelle Obama”, each accompanied by a thumbnail indicative of what the query will yield. After trying a few searches of my own it’s easy to see how this could come in handy, especially when it comes to searching for queries with multiple, very different meanings (like “Sierra Nevada”, the beer or the mountain range). That said, the feature is a little quirky – oftentimes I had to refresh the page if I wanted any suggestions to appear.

Meanwhile, earlier this week Microsoft’s Live Search introduced the ability to use an image itself to search for similar images.