[Q] Can't change boot image after flashing custom rom. topic

So, I flashed my Micromax Nitro A310 with a chinese rom based on MIUIv5 but that was too heavy for my device.
Along with the rom came this image (see attachment 1) that shows up everytime I power up/restart the phone.
Followed by the android animation (see attachment 2).
I have come to realize that the android animation can be changed easily via file explorers with root permissions.
But I have been unable to change the first image which although eye catching is not something one wants to see everytime their phone restarts.

So, My question is.
How do I change that image?
My device is rebranded coolpad F1 running on qualcomm.

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