A crucified person would be a good addition to the impaled bodies and heads. Especially for a Roman chronicles it would be helpful to tell some stories.
I would also love some ancient Egyptian and barbarian assets and hope they will come eventually.
India and East asia had a lot of assets additions lately and looks like South America could be next. I just hope we also get some new European and Oriental assets. They had a lot in the beginning of AoE2 but by now a lot is missing in comparison to Asia and chronicles. We have a lot of Buddhas and Indian god statues but only one type of stone cross for example. Also many city elements (markets, lamps, etc) that we have for Asia are not present for Europe and the orient.
Additional farms would also be nice (like in the event mode)