Same portals, two different photos, all wrong.
I have had the same issue for several days now.
I also have the same issue under the activities tab.
As you can see the green Lohkva Library picture is from portal korp! Arminia Dorpatensis; purple Rahumäe Cemetary Main Entrance and Tartu Linnavalitsus picture is from Vanemuise tiik; red Lohkva Library and Kirsi Rongipeatus portal picture is from portal Jüri Uluots and orange Love Hurts and Tartu Linnavalitsus picture is from portal Cityboy.