Invent what continues behind a covered Christmas picture
Keep the visible beginning of a drawing, then make your own continuation on another sheet. The hidden original can be revealed afterwards.

Prepare a picture with a clear beginning
Use three sheets and pencils or crayons: one for an original picture, one plain cover and one for your child's new version. One person prepares the original before showing it.
For a first example, draw a Christmas tree on the left and a blue curving path leading to a small house on the right. Keep the tree away from the middle so it can remain fully visible. This is an invented scene, not a map of somewhere you need to visit.
Put the plain cover over the right third of the drawing. Hide the house, but leave the tree and a stretch of path showing. The path should visibly continue to the cover's edge. Adjust the cover until those two beginning features are clear.
Copy only the part you can see
Place the covered original above your child's blank sheet, facing the same way. Draw the visible tree and path on the left of the new sheet, leaving the right side free. A rough copy is enough if you can recognize both features.
Keep the original covered while working. If the cover slips, put it back. Seeing the first house does not end the game; your child can still choose another destination.
An adult can help draw the visible beginning if copying feels like too much. Let the child decide what comes next rather than completing the new right side for them.
Give the path your own destination
Ask: “What could the path reach in your picture?” It might lead to a bench with a Christmas star beside it, a little house or something your child invents.
Draw that destination on the empty right side, then extend the path so it reaches it. Point along the whole route together. Does the visible beginning now connect to the new place?
If choosing is difficult, offer a bench or a house and leave time to decide. One destination completes the task; extra characters and snow can wait. Your child does not have to explain a whole story or guess what the first maker drew.
Compare the pictures only if you want
Finish the new picture before lifting the cover. If your child wants the reveal, show the original house and put the two sheets side by side. They share a beginning and can have different continuations.
Keep the child's drawing as they made it. The first house is one possibility, not the answer they needed to copy. You can also leave the original covered and end with their version.
Mark the backs “first picture” and “new version” if you keep both, so the two invented scenes stay easy to distinguish.