What do you write in the "showing time" field? 3?
You have to write the frames, so if you want 3 seconds you should write "180" (you will see the seconds in the right side). 1 second = 60 frames
About the picture... do you mean a background pic or one replacing the faces that you see to the left of the text?
If you want a background pic you will have to create a .fpg with the same name of the cutscene ("stage3g" for example). You won't see the background pic in Cutscene Maker even if is placed correctly, only in the game.
If you want to replace the faces... you can't, it's hardcoded in the game