Is it normal that for every change I make to my infra, any docker images are uploaded each time - even if the changes are unrelated to that docker image?

That is the current behavior, yes. The docker image resource runs every time.

Mm is there a reason for this that i'm missing? Or is it something in the backlog?

It's on the backlog - https://github.com/pulumi/pulumi-docker/issues/14.