Editing still images
As with other types of clip, you can trim still images directly on the Movie Window Timeline, or by using the Clip properties tool.
See Trimming on the Timeline using handles for a discussion of the first method. The difference with a still image clip is that you can extend it to any duration you choose, whereas a video clip can be no longer than the original Album scene.
Effects like Blur, Posterize and Color correction can be applied to still image clips of all types in the same way as to video clips.