My father has passed away. Who should receive the proposal party on my behalf?

Ideally your next wali (guardian), such as your paternal grandfather or full brother, because he is the one who will marry you off later. Your mother should still be fully involved; her views and blessing are very valuable. But in terms of proper order, it is good for the proposal to be answered together with the wali so there is no confusion on the day of the akad. If the wali lives far away, he can ask a male relative to receive the party and convey his consent. Make sure your own consent is heard before any answer is given. Losing your father does not mean you have lost your protector; the wider family can carry that role together. See the order of walis by lineage.