Fireforge had a funding campaign for 13th century Russian Armored Infantry that ended December 31st. Kit bashing those bits with gripping beast arab cavalry sets will create decent Baltic pagan cavalry, adding in gripping beast hirdmen heads and their generic dark age warrior sets should do the job. As for infantry, and shown in the pics above, the Gripping Beast Jomsvikings and Pagan Rus are the closest miniatures for Baltic Pagans. Keep in mind that Baltic cavalry used javelins/spears until adopting horse archery tactics/bows in the late 14th century. But since you're using the minis for a fantasy setting that might not matter.