Sure, you obviously don’t need the beast that’s shown there. But you still really don’t want a raspberry pi.
The CPU is only part of the problem. The other part, if you’re going to be storing a lot of pictures on there, is its I/O performance. You won’t even get full USB 2.0 speeds, because it runs your Ethernet off of the same USB bus. Even if you insist on doing ARM, try to pick one with USB 3.