After some experimenting and further research, I have disappointing news. It looks as though printing (maybe) acceptable-quality decals would need a fairly specialized printer (an ALPS) which is no longer marketed in the US, and which would apparently cost between $700 and $1200 US, best guess, to get going.
It might be possible to get short runs of decals printed by someone who already has gone through all of that. Has anyone looked into this? I may just be low on caffeine at the moment, but it suddenly seems like a high hurdle for a decal that may end up not being sharp enough to fool the eye...
With kind regards,
Josh, somewhat discouraged in CA
PS - in case it's worth going forward, what made it possible for the Pe De image to turn out (to my eye, anyhow) so much better than the De Ve image was the relatively high quality of Peacecup's original photo. It's large and it's at 180 dpi, and it's not rotated much out of parallel with the plane of the camera. I'd like to find out the height at center and width at the widest point of the original logo and make some (hopefully final) tweaks...