Yes, you can!
Changing the price of any image on your profile is as simple as going to the image page, and clicking on the 'Edit' button below the image. Here you can change the price (and other details), click 'Save' and your image will be updated.
STEP 1: Click the 'Edit' button on the image page
STEP 2: Enter the price you would like to set for your image and click 'Save'