I think your problem is that you are applying the retime to the compound clip. The problem is that when you do this you are retiming the compound clip as a whole, not each picture. This explains why you are seeing only 1 or 2 pictures, because you are cutting down on the length of time the compound clip is shown, not how long each picture is shown. You need to edit each picture. And rather than do a retime I would set the duration of each picture since retiming a still image isn't really necessary. Take the pictures out of the compound clip (or start a new project), put the pictures in the timeline, select all pictures in the timeline (CMD+A), CTRL+D (this is the keyboard shortcut for change duration of selected clips), enter in a numerical value, press return. The number you enter will effectively adjust the speed of the timelapse. By default FCPX displays the timecode as HH:MM:SS:FF so if you enter a one and a zero and then press enter the duration will be changed to 10 frames. The number of frames you want to choose for the duration you are setting will be up to you and the frame rate of the project. That should give you the result you are looking for. If you need any clarification I'll do what I can.
