1)Map on the wall
With nails and cord you can create a map on the wall with a geometric style in which you can hang photos, postcards, tickets or whatever you want.
2)Memories in a jar
It is one of the easiest way to do, you only have to looking for a jar with a perfect size for your objects. A good idea is to put 2 or more jars with different shapes.
Paint a quotation in the center of a wall and fill with photos of the best moments you lived in your erasmus. Surely it is an original way to decorate your room.
4)Box of memories
With a old wooden box, paint and a market you can create the perfect box in which save the best memories of your stay. They are beautiful and the are perfect to maintain everything in order.
5) Travel diary
In a agenda you can note every day what is happened, glue photos and tickets.
Buy a flag of Spain or Andalucia and decore it with some of the best photos; then ask to your friends to write something about yours friendship or a good moment passed together.