I believe the image sequence feature has been added to Vegas Studio.
File / Open, browse to the folder containing the images, click on the first one, and check the box at the bottom of the dialog box that says "open image sequence". Vegas will import the whole block of images as if it was a single video clip. You'll be asked what frame rate to use.
In order for this to work the pictures must be named with sequential numbers, like pic0001.jpg, pic0002.jpg, pic0003.jpg, etc. If you have a gap then Vegas will stop the import at that gap. Of course, you can then import the rest after the gap as another clip.