Nordic countries certainly, and Dublin (the ibis is in an abysmal location). Also Malta and Cyprus lack any Accor hotel. Batumi in Georgia has a property from almost every other chain / operator but Accor.
I would say the Baltics are appropriately covered for my needs - most cities outside of Riga and Tallinn in LV and EE are of minor importance and can be reached by a day's trip from the capitals.