create an image in your mind that...

[GoldfishLord]

Create an image in your mind that represents peace and calm. This will be your escape hatch for those moments when life feels overwhelming. Perhaps you feel peaceful when you look at the ocean, or maybe a field of flowers makes you feel calm. You may even visualize a cloud-filled sky to bring harmony to your mind’s eye. Take a deep breath and go to this place whenever the need arises.

Source: https://www.oprah.com/spirit/know-your-body-finding-peace-and-calm-daily/all

It is acceptable to move "in your mind" before "an image", so this makes me think that "that" refers to "an image", excluding "in your mind".
What exactly does "that" refer to?

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[Rover_KE]

Is it acceptable to move "in your mind" before "an image"?

Yes.

What exactly does "that" refer to?

An image.

 

[GoldfishLord]

Is "in your mind" included in what "that" refers to?

 

[jutfrank]

The pronoun 'that' refers to 'image', and 'in your mind' is the place where the image is created, obviously.