Theres a website called http://cdn.towerunite.com/ that the devs use to store the icons for the ingame items. But they added some icons for unreleased items, including some hats and things that may be in the summer update
Retro Guitar is used in Zombie Massacre already, but it could be an out of minigame item, since Zombie Massacre doesn’t have any icons from what I remember. Pilgrim Hat is already available in the hat section, and the miniature train car is available in Celebrations. Other than that, the rest aren’t released yet, so good find!
Heres a list of all of the items that could technically be put in your steam inventory right now, most of the new items are at the bottom of the page. https://steamdb.info/app/394690/items/