If prune face Palpatine is his true face and normal Naboo politician faced Palpatine is the disguise perhaps that globe thing from TPM is a power source for his mask.

Palpatine could have had access to it when it was in the Royal palace, used enough of it's energy to establish his alter ego and tried to obtain it permanently.

After it's given to the Gungans at the end of TPM it could be put on display in the Chancellor's office as a sign of the union between the Gungan and Naboo people and peace in general.

We see Palpatine has plenty of art objects in his office but these could be just a means of disguising the globe's true use.

When Mace goes to arrest him the globe could be smashed, making his true face come through and return permanently.

It would also serve as a metaphor for the shattering of peace.