I am currently running the "Lure of the Lost" and have recently completed the Begginer game "Mountaintop Rescue". I am wanting to add in an encounter or two to the parties trip into Reles in the wilds somewhere, but am lost on what kind of creatures would be common on spintir and what would make a good and memorable encounter. Any ideas would be greatly appreciated.

Here is a list for quick reference, but all of these are mentioned in the source material you have there. When you're thinking about creature encounters, think about what your goal is. Do you want a straight up combat encounter? Perhaps a chase (to run away form a stampede?) Don't disregard opportunity for taming/befriending a creature, or a hunting/style encounter to follow a creature to find water, food, or its nest/cave/home. Also, consider other various "skill challenge" encounters to endure bug bites or plant poison/rashes, environmental conditions, to navigate and traverse difficult terrain, etc.

If your goal is to provide encounters that give some wildlife atmosphere, you might do better with a few smaller non-combat encounters that only require 1-3 checks versus multiple combat encounters that require 10-20 checks.

http://starwars.wikia.com/wiki/Category:Creatures_of_Spintir