No. I don’t think you are being petty at all.
You put in loads of original effort and were generous enough to share it with the world.
This spanish guy has obviously used your specific design (and, originally, your photos) without honestly stating attribution.
Not only that, he is now denying it is your design!
But your design is so distinctive, there can be no mistake…it’s yours!
I am so sorry there are such selfish folk.
I hope he makes no money from this ebay ad.