I have some X-cepters I purchased some time ago. I like image attached to them. I recently purchased a few more. I want to change the image of the new ones to match what I already have. The image is not one of the public images. How can I change the new starfighters' images match the old ones?

You would have to find the original artist and ask them to share it with you for your new ships.

Maybe posting the image you have in the arts part of the forum draws out the artist?