VHIStudio is the only way I'm aware that you can grab images from the tvcard.
Unfortunately, although a demo is available, VHIStudio is a commercial product which you will have to register or else your grabs will be stamped with the word "DEMO".
On the positive side, being a registered owner of VHIStudio myself, it does a FANTASTIC job of high speed shutter-like grabs, and you can also grab a sequence of video that will compress to a Quicktime movie.
However the downside of the QuickTime grabbing is that it doesn't sample audio into the .mov file...but the compression and conversion is quite nice and fast on my 060 setup, better than previous versions that compressed to MPEG which took FAR LONGER to compile the video.
The VHI driver should be on the MMCD and certainly in the MM_CD_Updates.