Bit of an update, there is now a general licence for all my stuff:
“Unless projects are accompanied by a different license, Creative Commons apply (“BY-NC-ND” for all art featuring the Canine mascot and “BY-NC” for everything else).”
It’s even included on my website, where most of the demand for a clear licence originated from:
In practice this changes nothing, as I was never enforcing anything more than this anyway and given permission for other use too. Now it’s just official that this is the baseline, of what can be done, without having to ask for permission first.