Yes, you can.
Go to the coupon overview, edit the coupon.

1)
Make a very small change to your coupon title or subtitle by going to the Homepage on the left menu of your coupon builder.
Save it

2)
Remove your last update and save it again.

3)
If you now go back to your overview, you'll see a "preview image coming soon" screen for that specific coupon.

After 5-10 minutes you should see a new correct preview image.