When you assume a XPHB form, you can choose the form of an Animated Object created by the Animate Objects spell. You choose the object's size (up to Large). At Druid level 10, you can also shape-shift into a Huge object.
Object Shape
Raw data
{
"name": "Object Shape",
"level": 6,
"__prop": "subclassFeature",
"header": 2,
"source": "ValdaPlayerPack2",
"entries": [
"When you assume a {@classFeature Wild Shape|Druid|XPHB|2} form, you can choose the form of an {@creature Animated Object|XPHB} created by the {@spell Animate Objects|XPHB} spell. You choose the object's size (up to Large). At Druid level 10, you can also shape-shift into a Huge object."
],
"className": "Druid",
"classSource": "XPHB",
"subclassSource": "ValdaPlayerPack2",
"subclassShortName": "City"
}