These are definitively Aerial bombs and not mortar bombs - one is also present this other photography of air bombs (supposedly taken at the bombs depot at Salonique airfield in 1917 - this would make identification as a "Bombe Claude" doubtful as these bombs were, as far as I know, withdrawn from service in 1916, as being too unsafe for the users....). What is interesting is what seems to be a filling opening on its upper side.
A wide range of other artillery shells transformed into aerial bombs can also be seen on this photo :
in the foreground 2 obus Michelin (115 mm? or 155 mm?) (the fuze is similar to the one commonly seen on the 75mm "obus a balles")
then another "square section" bomb
2 120 mm obus Michelin (?) (or may be 122mm Gros Andreau, though their body seems rather cylindrical)
3 bombs made from "obus de 90 mm" and 2 from "obus de 75mm"
And on the boxes "obus de ???
So..what can these "square" bombs be? incendiaries?
As for the Trench mortar bomb 150 mm - the 150T bomb has only a superficial similitude with these bombs -
moreover ...this mortar bomb was introduced only at the end of 1917 while the first photograph is from 1915.
Here 's a picture of the 150T mortar bomb - modele 1917 (the initial 150mm modele 1916 was very different)
