Question

What is the subject of these sentences?

How much do you remember from that display?
You or display

Near the satellite model was a large picture of Jupiter.

Are you searching for the gift shop?

Answer 1

1. Display is the object of a preposition -- so it is not the subject. You is the subject.

2. What was?

3. Who are searching?

Answer 2

So picture for the second one
And you for the last one?

Answer 3

Yes; both are right.