For starters, SO stoked to see one of my images used like this. Thanks for choosing it.

Patterns registered for a template part should be interchangeable via the UI. Or, parts that use the Pattern block should display correctly in the “Replace” dropdown.

There's lots of issues open around "displaying contextual patterns", including this one: https://github.com/WordPress/gutenberg/issues/28739

What you're describing feels like it falls into this work. Essentially, you want to see patterns more prominently displayed when folks are working with templates and template parts. At the risk of overwhelming with issues, I'll point out the following two and leave it there:

https://github.com/WordPress/gutenberg/issues/28737
https://github.com/WordPress/gutenberg/issues/27575

The long and short is that this work is underway to better display patterns both when starting blank and when actually editing current content so you can see at a glance what other options might fit nicely exactly where you're editing. There's obviously a substantial amount of work to get there :)

Can't wait to see your theme out there (along with Otto!). Ship away -- it's paving the way ultimately and I'd love to see a diverse take on block themes.