Lennon Wylie - another Lost Album - https://www.lennonwylie.co.uk/LostAlbums_NOInfo5.htm
Various family names in play, unknown connections if any.
"Wm. T. Shanacy(?) May 1892 Aetat 25 - To L. Shanacy(?), Glasgow - Mount Gambier, S.A. Photographer"
We have a name, date and place (Southern Australia) so this should be very easy to determine. "Aetat" is improper Latin for 'age' so he was 25 when the photograph was taken.
In the South Australian Directory (Sands) from 1922, we have Dr. William T. Shanasy, J.P., dentist - 168 Childers St, North Adelaide.
He studied dentistry at the University of California no less. He is described in dozens of trees on Ancestry - William Theophilus Shanasy or Shaughnessy (b. 1866 , d. 1922) . This ties in with him being 25 in 1892.
I'll not pursue this any further unless links to other lost photos emerge.
Who is the L. Shanacy in Glasgow ? Is that Glasgow in Scotland or is there one elsewhere ?
"Catherine Ester or Esler? McLallan(?) 7-2-93 - With love & fond wishes of the original"
I suspect the name is McLellan or perhaps Callanan. Even if we find someone with that name - and there are possible candidates - you can't prove it is them without additional information (like the date being significant or if there's another photograph of them).
I agree that the reading of the text looks like Delihurst - it looks too long to be Delihunt. Dewhurst is also a possibility. There is a rare surname 'Dellahurst' and while you might think that this makes it a perfect 'genealogical' surname, the spelling variations may confuse it with other names. There are no examples either in the 1901/1911 census records or the BMD index.