Using stock images in open source project

Question

I have started an open source project and would very much like to have a cute and catchy icon to label the project with. My dilemma is that I have little to no experience designing vector graphics for use in such a project. To compensate I thought I might purchase a graphic from one of the stock photo service (shutterstock, etc.).

My project produces HTML documentation from Gherkin language files and my intention was to use this icon on the footer of each page for an "output produced by ..." kinda thing.

My question is what implications would it have on my licensed software if I were to use this graphic in it. I am releasing the software under the Apache v2 license.