Do scriptures allow to worship idol/photo of an acharya/guru?
yes, they do.
Sri Krishna in Gita:
ब्रह्मचर्यमहिंसा च शारीरं तप उच्यते।।17.14।।
So He mentions Gurupuja as one essential part of tapasya.
Guru and deity should be respected equally.
Dhyanamulam gurormurth (Sri Sri Guru-Mahimamrita, ie The meditation of image of Guru is the highest meditation.
Gurupujaam vina devi ishtapujam karoti yah/mantrasya tasya tejamshi vairabhah harate swayam.
Gurupujaam vina naatha kotipunyam vrith vyayam.
All of our scriptures make Gurupuja essential before every worship for initiated people.
Reference: Sri Sri Guru-Mahimamrita, Omkarnath Rachanavali,vol 9, page 1-199, THE ENTIRE BOOK IS ON GLORY OF GURU)