BIP-110 is one example but there are many use cases for using custom images, like when you build your own from scratch. By default OrangeLab runs standard version of Knots (or Core), not the custom one. One might argue that promoting protocol change to increase OPRETURN from storing hashes to storing data is shitforking 😉 Node runners have an incentive to keep things light on resources, both storage and bandwidth. It's a matter of negotiating how far the validation rules should go. In the end it's up to node operators to decide what a valid block is. You're welcome to run any image and version, I'm just making it easier to do regardless of what you decide.