Hahaha, don't feel bad. Even I miss out on things like that all the time. OTL
Hm, since our standard decks are 20 cards a piece there should be--at the very least--21 pictures in any deck donation (the 20 cards + a master badge). Anything less than that wouldn't work as it wouldn't fill out a complete deck so I'm going to say that yes, you should choose a photoshoot with more images but at least 21!
Re: idol factory tasks
Hm, since our standard decks are 20 cards a piece there should be--at the very least--21 pictures in any deck donation (the 20 cards + a master badge). Anything less than that wouldn't work as it wouldn't fill out a complete deck so I'm going to say that yes, you should choose a photoshoot with more images but at least 21!