Online image repository accessible from C#

Hello.

I'm developing an application that will need to download images related to some specified keywords. What i need is a list of online image repositories and image search engines which can be accessed from C# (by using API specialized for C# or some other method).

The service needs to be easily accessible, without any registration necessary. ATM, i'm using YIS API (Yahoo image search), and the problem is - it's too slow. It needs 3-5 seconds before it starts displaying anything.

I would use GIS, but i couldn't find any relevant API for it.

Do you know any similar services that can be accessed and that allow keyword-based image searching and downloading from within C#?

Thanks.