This is a super idea for a kid's birthday party.
Having a party based on the theme of a movie isn't new, but having one that is all about the Norse kind of life and dragons is.
There hasn't really been anything in the rage about Vikings, especially in the party scene.
But just imagine if you were the first ones to set the new trend.
You might try:

• Picking up a pinata that is shaped like a dragon and filling it with all kinds of fun things.
  Candy goes into it for sure, but you could find little plastic dragons and vikings and stamps and pencils and erasers and a myriad of other trinkets to fill it with.
  
• Of course you need balloons and streamers, too.
  You can make some really 'rough' looking streamers from old brown paper bags.
  Just cut the bag open so that it makes a long strip, and then twist them up and then tape several together to form 'ropes' that you can string from one end of the house to the other.
  Or, coiled in a corner might be better.
  Straw makes a great addition to this theme in decorating for the party.
  
• Draw dragon shapes on cardboard and cut them out and tape them on to the walls.
  Use several different colors of posterboard for different kinds of dragons.
  
• Make 'Dragon' punch.
  This can be lemon lime flavored punch with some dry ice floating around in it.
  Add some lime sherbet if you want it more creamy.
  
• Cut out 'dragon tracks' out of cardboard and lay them all over the driveway and entryways.
  Maybe even put some up on the wall.
  
• Have the kids go on a hunt for the dragon (which is the pinata), sort of like going on a safari.
  Put dragon tracks all over making a trail, and have them follow them through all kinds of obstacles to get to the dragon.
  Or, you can play 'Pin The Tail On The Dragon'.
  
• You can make a dragon body and cut out either the face to let the kids put their faces into the holes to take pictures, or make one and set the kids next to it to take a picture of each one.
  
• Gather Norse themed items to display around the party area.
  This doesn't have to be expensive or time-consuming.
  Simply draw or cut out simple designs on cardboard.
  
• Make a cake shaped like a dragon.
  

It would be great to have a party that has a unique theme.
Just have fun with it.