Workflow:

Collected images of age of empire buildings, some i found online, others i extracted directly from the game

Replaced the alpha channel with a flat green background

Dreambooth fine tune using the same service (https://dreamlook.ai/)

Loading the model in automatic1111 and generating and picking images, more or less with the default settings

I used https://clipdrop.co/ to remove the green backgrounds to make them transparent again and pasted them on some AoE style terrain