You can just extend the images for more frames in their scenes if you want them to appear longer.
If your file is an AS3 file, then you can change the frameRate using actionscript.
It is not clear what the intention of your design approach is, so explaining that could help point you in an entirely different direction for your design.
Change the frame rate dynamically:
or just add a few extra frames if you want one image to display longer... so instead of displaying each image for one frame, some display for one, others for two, etc.
Also, if the audio is intended to sync up with the images, realize that any change in frame rate will throw this off.
then added the sound
If you do plan to sync the audio, you may have to add the sound first and then match up (add) the images to the audio... or you could be looking at problems.
The design is intended as a memorial .... it is composed of 35 seperate files some of which include written memories and the others just visual images.
When I was doing the design I tried to add them as seperate image files however I didnt seem to be able to make the images fit the stage area correctly and when I tested the SWF file the images were all cut off in strange places and so forth so I looked at other options and found that I could add each image in its own scene which I did but now have the problem of the FPS rates.
Now just to explain a little further:
Img 1 has text and needs to display for at least 20-30 secs.
imgs 2-4 are visual only therefore only need to display for say 5 or 10 secs.
imgs 5-8 have text so they need to display for at least 2-30 secs.
and so on through to the last image.
Hope that makes more sense now ?
With those kinds of delays, I would not deal with this in terms of manipulating the frame rate or the number of frames at all. You should build delays into each frame using code. Also, do not use scenes, just place the images one frame after another in the first (and only) scene.
Then what you can do is have one layer with code that will extend across all frames so that its code is shared. In this shared layer you could have the following code:
Then have another layer for actionscript where you have code for each frame that resembles the following...
sto = setTimeout(playOn, 30000); // 30 seconds delay
The stop makes the animation stop in that frame.
The sto line starts a timeout function that will call that playOn function after the time specified passes (30 secs in that example - the value is specified as milliseconds)
You could also use a Timer instead, but the setTimeout is probably simpler for you to deal with.
If you are running into a wall trying to use code to solve this, then just use the timeline. Set the framerate of the file to 1.00 (1 frame per second) and extend the images for as many frames as you want them to have seconds of display time.
If you want the first image to last for 30 seconds, extend it for 30 frames.