Hello!
This guide was made after I noticed there was no guides on Steam for collecting all 10 treasure chest bonus images. My goal is to create a quick reference material to check at any time.

This treasure chest can be found a little ways inside the Town Hall, directly to the left of where Chief Wulf is standing.

To find this treasure chest, you'll need to start Stumbler's Minigame and go into the tunnel past the door to the second area.
The chest will be at the back of the tunnel, next to some crystals.

This treasure chest can only be found in the 1997 version of the game.

After failing Giovanni's minigame once, enter a second time and the left side of the roof will be replaced with a glitching texture that you can jump through.
The chest will be against a wall immediately in front of you.

This treasure chest is inside Olive's minigame, placed against the side of the connecting hallway between the two areas.

This treasure chest is waiting in The Hull, the area below the stairs on the beach where you start the game.

This treasure chest can be found next to Walter Walrus, you can find him standing near the back of the Living Quarters

This treasure chest is placed at the end of two rows of houses in the Living Quarters, directly ahead of the door leading to the beach.

This treasure chest can only be found in the 1997 version of the game.

After failing any character's minigame 3 times, let time pass until midnight and head into The Theater. You'll now be able to pass through the left side of the back wall and enter an upstairs passage.
The chest is at the end of the passage, against a wall.

This treasure chest can only be found in the 1997 version of the game.

After entering layer 4, go through the first door and enter the Render Distance Corridor.
The chest that you're looking for is the 10th chest on the right.

This treasure chest can only be found in the 1997 version of the game.

Once you've progressed into layer 3 and arrived at The Plaza, head for the Gallery as marked on Stumbler's map of the area. The chest is against the back wall of the room

The gallery is a second set of images that only unlocks after you've completed the True Ending of the 1997 version at least once.

Thanks for reading me! Toodles!