I made the layer styles into their own layers and grouped the layers for each inset composite image in their individual folders so that editing would be easier. This approach would also make it easier to create matching borders.
By changing the layer styles into their own layers, the images can be masked without having the layer styles cause unwanted, unrealistic effects.
Because of the reduced size of the inset images, they are likely to appear sharper and more dynamic that the large background image. This should be addressed by the method of image size reduction, noise, and maybe even softening until they compliment the original.

forum discussion: http://forums.dpreview.com/forums/read.asp?forum=1006&message=29241248