On my desktop the Twain driver for my Epson scanner has a lot more control than the WIA driver so here's a Twain library. The WIA drivers are also available through Twain.
There may be a memory leak associated with converting DIB bitmaps returned by Twain to .NET Bitmaps. If there is I haven't a clue how to stop it as I am pretty ignorant about native code graphics and memory allocation. EDIT - Sorted for the release version(I think!).