Same problem and still no fix in sight because Apple has moved on with iMovie and left 9.09 users with a broken product that intermediate editors can not use.
A down and dirty work around to the black still picture problem with imovie 9.09 and El Capitan, if you are currently editing a project, you can pull the still photo or document up into Preview window, launch a screen capture product like Viola that can capture video from the screen. Set to record a region - set the region the still picture and hit record for about 8 secs, stop recording and move the now video clip into a folder and then drag and drop to iMovie. Now the "still" video will be visible.
When I tried to add a title to a clip - iMovie crashed - no fix for that problem - looks like the iMovie Pro/Am editors will have to pay and learn to use FCP to kill the mouse with an elephant gun.
Or the best way - get a copy of Yosemite and wipe your hard drive and reload Yosemite and your apps - hopefully all your current projects and events are on external drives.