Maybe you have a special message for your teacher. Then this is a nice way to express it. If you are not a wordsmith, then you can just borrow a special quote. You can also include your artwork if you want.
This is another good option if you want to use your class photos for your photo art gift to your teacher. The best thing about this photo art is that it allows you to use bigger pictures. You can put individual photos of the whole class.
Instead of a portrait of a house, you can put a portrait of your school building. A perfect gift for retiring teachers so they can always remember the special place where they worked most of their lives.