You are welcome to download and use the creatures from Creature Party as you wish, provided that you follow this “Be Nice License” (BNL 1.0). As the name implies, the idea is that in return of using the images, you will do something nice for someone else. You get something nice, you pass on something nice. There is anyway too often too little niceness in this world. A bit more would help.
Examples of what the creatures consider to be nice: