snapper? glowworm? на сленге

I’ve never heard those

'glowworm' is hard to find in dics but snapper is registered in Green's Dictionary of Slang:
"also shutter-snapper
[SE snap, a photograph]
(orig. US) a photographer."

Maybe 'snapper' is obsolete?

No idea. I’ve never come across SNAPPER in the sense of photographer in any old books, old movies, or old shows. The only slang reference to SNAPPER that I have is to the vagina. Same with GLOWWORM. and I dare say that if you referred to someone in terms of “he’s a real glowworm/snapper“, nobody would have any idea what you were talking about.

Celebrity snapper

"Celebrity snapper Rankin focuses on death in online show"

"The playful shots were found in the loft of the celebrated fashion and celebrity snapper, taken in impromptu sessions at the end of two official photoshoots in 1976 and 1993 - the first of which featured McCartney's band Wings, which he formed with Linda."

(Dailymail)

The Duchess of Cornwall celebrated her 70th birthday with a photoshoot by celebrity snapper, Mario Testino.(Mirror)

I guess they say that in Britain.