Emphasis: before and after

After: above; Before: left.
Emphasis:  I saturated the banana with purple, the compliment of yellow to give emphasis to a single banana on the clump.  Then, I added some patterns to add further excitement, rather than change the size or shape.
Harmony:  Next, I cutout the bananas and inserted them onto a background of similar patterns and colors to add harmony to the picture.  Not that it was needed, but I thought it created a more interesting still life.