I am authoring images in another program - POSER - for importing into Vegas Pro 2012.

I am doing so at 24 fps and that is how I have timed it.

When I set up the property timeline does it really matter whether or not I use a 23.976 timing or should I change the frame rate to 24 fps?

My output will be the web and/or bluray. Thanks!

if you're exporting an image series it shouldn't make any difference....

For the web you could go either way. For Blu-ray, you need to stay with straight 24 fps. So, I wouldn’t change it.