I might be a bit late but I'll post a solution for others who have faced/are facing a similar issue. So basically what you have to do (at least for the solution you are seeking, i.e a custom image imposed on a box-like background) is impose the customImage on the background box with the help of a canvas. Using this implementation you can effectively create a BitmapDrawable from the canvas that you can then assign as a marker for your 'Overlay' / 'ItemizedOverlay'.
Also, please refrain from creating an ImageView for each overlay as this will utterly destroy your memory/ your app if you have to deal with thousands of such ImageViews simultaneously. Instead, use BitmapDrawables that can be assigned to the overlays during their construction and don't consume nearly enough memory as an ImageView.
public BitmapDrawable imageOnDrawable(int drawableBackground, Bitmap customImage)
{
//The following line is optional but I'd advise you to minimize the size of
//the size of the bitmap (using a thumbnail) in order to improve draw
//performance of the overlays (especially if you are creating a lot of overlays).
Bitmap customImageThumbnail = ThumbnailUtils.extractThumbnail(
customImage, 100, 100);
Bitmap bm = BitmapFactory.decodeResource(getResources(), drawableId);
bm = Bitmap.createScaledBitmap(bm, 112, 120, false);
Canvas canvas = new Canvas(bm);
canvas.drawBitmap(bm, 0, 0, null);
// The 6,6 in the below line refer to the offset of the customImage/Thumbnail
// from the top-left corner of the background box (or whatever you want to use
// as your background)
canvas.drawBitmap(customImageThumbnail, 6, 6, null);
return new BitmapDrawable(bm);
}