There are no excuses.
Listen. Let's start again.
1) I was in good faith. I never intended to steal anything. I assumed (wrongly) that because the download button was present it was ok for you that people download the image and use for personal use, like windows background or similar. I printed a single copy for my house. No selling, no commercialize.
2) My good faith is testimonied by the fact that I came here to show you (the author) some love and the result. If I was not in good faith I would never do this. Just steal and run.
3) You attacked me as I was a thief and that caused my bad reaction. I apologize for not having asked your permission in first place and for insulting you.
4) I totally agree that authors must be repayed for their work, and I'm totally fine to reward you with the correct price for the image. Let me know how much you think is fair and I will pay you via paypal or here on this platform.
Hope we can close this as friends and not enemies.