I am trying to insert an image into Stellar private network. I have gone through all the operations but did not find anything.
Any new update with Stellar protocol version 12?
As Orbit Lens already said, Stellar is not suited for this purpose. However your best options for storing data are:
ManageData Operation: 64 byte key + 64 byte value, but will require a 0.5 XLM reserve per entry. To eliminate the reserve requirement you could delete the entries right away but since Stellar is a state machine that (other than e.g. bitcoin) does not need the whole complete transaction history for progress, that data will only be stored by full archive nodes in long term. Besides I remember a year ago there have been discussions to deprecate the ManageData functionality at all.
Transaction Memo: 32 byte (again, transaction history is only stored by full archive nodes)
SetOptions(HomeDomain) Operation: 32 byte (same downside)