Basically all my images and other media uploaded here can be used "as if" in the Public Domain (PD), meaning you are free to use my images in any way you want without asking permission, paying fees, attributing them to my name or whatever. For some countries this is not legally possible so you may apply a Creative Commons Zero (CC0) public domain dedication.
However, I do appreciate knowing about the usage of my images and if you feel you want to credit me that's fine too of course. I just want to give you the freedom to also use the image without contacting me and to not bother with credits if this would break the lay-out of the project you're working on - The choice is yours.
If you even have a budget available for the images to use in your project, you may want to consider spending some of it on a voluntary donation to the Wikimedia projects. Thanks!