A gallery displaying all included graphics/ images. I use Adobe Bridge for this, but having it incorporated into InDesign would be snazzy.

The feature would be very handy, if one has to pull out and rearrange a large number of graphics, to just drag them out from and then back in to the spread. If they are placed out on the pasteboard, I often 'lose' them and have to scroll up and down to find where they are 'parked'.

I have had to drag all the graphics out