How do I change a series of fruits and vegetables in a shape of a kidney?

Refinement of an Outline:

Use much smaller fruits (like blueberries or cherry tomatoes) to perfect the outline of the outer curve of a kidney to make it more precise. 

Arrange leafy greens such as spinach or parsley on either side to promote smoother transition along edges. 

Color Coordination:

Clouded colors while in a group, such as with gradient or pattern: 

Arrange for example; put green vegetables (such as cucumbers with broccoli) on one side and red/orange items (such as tomatoes with carrots) on just the other. 

Adding More Detail :

Structure toward center thin items such as green beans, asparagus, or even carrot sticks to imitate the anatomical feature perhaps resembling the renal arteries or veins. 

Such small round items forms the smaller complicated structures such as grapes or kiwi slices. 

Background Contrast:

New surface is either neutral or contrasting to render a more distinct shape for the kidney. 

Visual interest will be enhanced around the kidney by adding edible garnishes such as sprigs of herbs. 

Scale:

If you find some fruits or vegetables too big, make them smaller so that they fit well into the shape. 

Visit Harvest Fresh for More Details.

Use liquify. Just google liquify and see the options.

Since the content of the fruit and vegetable image is generic, rather than work with the file you supplied, key into Google Images "fruits and vegetables" and choose from the many commercially available stock images similar to the one shown here. The time you will save is considerable and quality will not be in jeopardy. Place the image on a layer below the kidney illustration and mask the kidney area to reveal the fruits and veggies. You can slide the content within the mask to choose the most pleasing array and alter the size of the fruits and vegetables image, as well.

Place in cutout fruit and vegetable smart object layers.  Use the Place transform to size and position the smart object layer around your kidney shape. Overlap them using layer stack order. Each layers can be duplicated and each have its own layer transform while sharing a single fruit or veggie object,  Transforms can also distort layer so the size and shape of a object can appear to be different.