So, my CreateFileA call in win32_handmade.cpp fails to find the path specified (When I put them in handmade\data\test). I noticed that if I moved all the images to a place relative to my built .exe instead, everything loaded fine.
I have a vague memory of Casey showing us very early in this project how we change the default data directory for where it looks for resources, a VS solution technical thing iirc.
Could that be it, that I have lost that setting? If so, if anyone feels helpful enough to point me to the episode where he sets it, or just tell me how I should set it, I'd be happy!
Until then I'll just have my resources at the default relative location. :)