"I will take one hundred pictures."
No, that is not the verb.
百まい = "100 items of" (refers to the number of pictures)
とります = "will be photographing" (the verb)
しゃしん を 百まい とります
[picture] [object marker] [100 items of] [will be photographing]
Subject = "I" is implied by default
hence, rearranged for english:
"I will be photographing 100 items of pictures"
Translated to proper English:
I will take one hundred pictures.