You mean you want the stills to have less time on screen? Right click the first still. from the submenu, select "select events to end."
Now all stills are selected. Press "G" for group. Now all the stills are grouped.
Go to the last still. Hold down CTRL and while doing that, click on the right edge of the last still, and drag to the left. This will shrink the length of all stills on the timeline by equal length. Your pans, etc will still be in place, although you've also changed the end target point of your keyframe, so you may need to adjust some of the images.
You can also use Ultimate S to simply shorten the length of all stills while adding motion, transitions, etc.