Imagine you were using some of our pixelation tools to create an image and you posted it online for your friends to see - but, a week later you find out someone took that image and put it on a T-shirt that they're selling for $10 each.
Now that we understand Copyright, what would need to change in order for the scenario from the warm-up to be okay?

What I would need to change for the scenario from the warm-up to be okay is for me develop a CREATIVE COMMONS LICENSE

Explanation:

Based on the information given what i would need to change for the scenario from the warm-up to be okay is to go ahead and develop what is called CREATIVE COMMONS LICENSE reason been that this type of licence will enable the public to use or have free licence to the work that I have created by using it on their own product or items which in turn will enables them to as well sell their work which have my own work on them easily and freely without any form of hindrances.