Something like this?

Create as many formula fields with the code displayed like above as needed but increment the highlighted number.

Let me explain: the first line 'let currRec := this;' puts the current records'ID in thge variable currRec.

In second line 'select Customer where ParentOfCustomer = currRec' i create an array of all the records linked with the current record and with 'item(select Customer where ParentOfCustomer = currRec, 0)' I select the first recordID in line of that array (arrays starts counting with zero)and put it in variable i with let i:= ....

Third line, with
record(Customer,i).Photo
I pull up the Photo.

Steven.

PS: Used example database is the built-in Invoices template

Sure, here it is....

https://www.dropbox.com/s/cmiytrif694x2oa/Enhanced_Invoices.ninox?dl=0

Steven.