You may wish whatever you like Pikachu-san. Some people wish for big things like "world peace" or "I want everyone to be happy" while some people wish for small and personal things like "I want to get into this college" or "I want to be in love". There are times when people wish for other people such as "I wish that my friend's pet will feel better" or "I hope that my cousin's job goes well".

It is all up to the person wishing.