Any ideas/problems/guidance/thoughts would be
appreciated...

Shops often suspend pictures by wires that run from ceiling to floor -
would it be possible to adapt something like this ?

....something like a small channel iron hard up against where the ceiling
and wall meet - you could vary the width by sliding the "hanger" drops
to suit...

The fixing in the channel iron could be something as simple as a washer
or coin with a hole drilled in it (anything wide enough to stop it
sliding out of its own accord) with a length of cord knotted on one side

Forgive the crap ascii art below, but it might give you an idea what I
mean... (the hanger

_________CEILING_______
|| _&_ |
||_ { _| - channel iron
| }
| {
W }
A {
L O - drop and picture fixing
L
|
|