Setting Random Positon(X,Y) of a object through XML

You seem to have understood well the first few points - because you gave answers to them.

To explain more thoroughly my last point...as a concept its quite simple: Imagine your images were exactly sized to fit on the screen in a 2 X 2 grid... so each image was the same size and there were 2 across, 2 down - completely filling your screen. You can now randomly place 4 images in each of the set locations... a grid or table (in this case a 2 x 2 grid). If you did that then they would not overlap and you can fit 4 images on screen. But if I randomly place one image and it doesn't go completely in one of the grid positions... then it will limit the number of images that you can place - you will never be able to place 3 more (without scaling down). After 1 image it might already be impossible to place any more in this example. The same principle applies in a smaller space, with larger numbers of smaller images where you don't constrain to a grid layout - and you don't permit overlapping.

In terms of solving it... well I'm not too sure... I've not had to deal with it myself before. Depending on the number of images, their size and the space have to put them in... sometimes it might be OK and other times not.
If you want all the images to be displayed then (I think) you need to make sure the size of the images is such that you will always be able to place the number you want even with the most inefficient placement possible (even if its not very probable from random placement). In the example of a 2 by 2 grid I believe the most inefficient placement of one image would be in the centre. But by using this as a reference and reducing the size of the image until you get to a size where others can be placed around it then you should be able to fit 4 on-screen again with random placement. I'm not an expert at this stuff (not at all). I guess I'm trying to understand it a little better myself...and probably over-complicating it in the process. I've always done random placement to grid locations in the past. Anyhow perhaps others can advise whether some extension of this approach can be used to determine image size for a given number of images and a given space to allow true random placement of all the images under all circumstances.

Also looking at your code I see what you mean about it being static and understand why you want to change it.

You should make more use of loops and dynamic naming of the clips you load into.
I also suggest using the MovieClipLoader class and the onLoadInit handler for each clip. This will be the best place/time to resize the images if they are different sizes as you say.

I would like to be more specific, but I think you need to start with that and get things working that way first. And in terms of the random placement - assuming you have a number and size of images that will always fit in the space when allocated randomly... then I can think of the easy way (which is not very efficient and could get stuck working on placement for some time if the spacing was tight)
1.
a. choose random x and y coords and check if it is occupied (e.g. hitTest all previously loaded images). If yes go back to start of (a) .
b. check the random x coord+image width, y+ image height... is it occupied (same again) ? if yes go back to (a)
c. place image there.

To do it more efficiently perhaps someone else has some existing code to track placements and limit the selection of the random points to the space that is not currently occupied.