Of course, one of the main things would be James Cameron's Avatar.This was a visually amazing film and I personally thought that the environment design was astounding. All the creatures were very unique, as were the many plants in the jungle on the planet. This is a great inspiration for my level and it motivates me to come up with the designs for an alien ecosystem.
Some things to note about the creatures, they all seem to have three pairs of limbs, this is a common trait on most of the animals seen in the environment. Plants are colourful and very large in size. There is also a lot of focus on how the plants and animals look at night. They all have almost fiber-optic looking spots on their skin; bioluminescence is one of the main trends of the environment. Even the grass has a glowing effect when in contact with a living creature, I guess a reaction to their electromagnetic fields or perhaps heat alone.
There is also Blackreach in Skyrim. This is one area of the game that is underground and has lots of giant glowing mushrooms. It has a very interesting atmosphere.
Another game with interesting colourful plants and environment is Guild Wars 2 in the Grove area. It has some very interesting plant designs and it has a very vibrant feel.
I would also like to point out the Jim Henson film "The Dark Crystal" made in 1982. They had made some really interesting and unique environments, and the video below shows one of the best scenes in the film to show this. The uploader designed their own audio for this as a project, but it does show the exact scene I wanted to point out.