$1000 USD over a 2-4 month span.
EDIT:
My obligations would be full, but gradual removal of AI generated art assets. The investment would be solely used for the replacement of AI assets with human-created art and the facilitation of that specific process (ie, hiring and funding artists). If all assets are replaced and funds from the investment remain, the remaining amount may be used to produce/procure more human-made artwork. If there is no further need for art but funds remain, the remaining balance may be used for other aspects of game development.
In short, I'd paid for you guys to get human-created, handmade images. You'd replace the AI "art" with human work as often as you get it. Whatever money you have left is pretty much up to you to use, so long as you don't include AI art assets in future builds.