When using stock images, you have to know that these are used by many others as well.
When creating advertising, however, you should pay attention to an individual design. Therefore, you need to edit the images and give them their own look.
Here's an example:
Used stock image from Fotolia:
You can use Adobe Photoshop or Gimp to do these changes.
If you need help, please follow and contact me.
Have all a great day!
Norbert