For example, in Greek Mythology, there were a race called The Myrmidons. They were ant-people, and were very skilled warriors. The Greeks probably got the inspiration for this creature from the fact that ants march, similar to an army. Ants also have exoskeletons, similar to the armor of the ancient Greeks. These observations are basically just metaphors or similes comparing an animal and something many people know about ("The ants marched like soldiers across a miniature battlefield" is an example of this). You can find many more of these comparisons in poetry.
The above link will take you to a random page on the animal wiki, a database of animals. When I want to create a new race, sometimes I will go to this wiki and press the "random page" button.
A list of legendary creatures If you are going to use these methods, remember not to be offensive to someone else's culture. Do research on any civilization you will base a creature from, or it may appear stereotypical.
If you have a dream, you could implement it into a game. You could use this method of inspiration to come up with any aspect of your game.
You may also want to edit your creature even more. If so, think about the role of your creature in the game. Here's an example: I want to create an evil race for enemies in my game. I base them off of bats, but I want to add something to them, something that will really tell gamers, "Look, this is an evil creature!". Think of things that are generally associated with evil. Not terrorist evil, but something more...superstitious. Superstitions cause people to associate darkness, mist or fog, and fangs as creepy or scary, and I want to make my bat creature scary. So here's what I'll do. I'll add fangs to my bat creature, I'll draw mist or fog pouring off of it, like a phantom, and I'll place the enemy in a dark level in my game, like a cave (Which is the bat's habitat at night). Seems like a good villain or enemy character, right?
If you have trouble designing the layout of a location, use the layout of your house (for a dungeon of a cave) or of your neighborhood (for a bigger location).
If you're programming a sci-fi game, get ideas from Antarctica (or another place similar to that) to design a planet like Hoth. If you're programming a fantasy game (like World of Warcraft), then get ideas from North America for evergreen forest locations, or from Latin America for tropical locations. You could also get ideas from Africa, the Caribbean, Asia, and Europe. Any place on the planet could give you inspiration. Just do research on your target country or continent before modeling a location after it.
If you're programming a sci-fi game, you could use the sci-fi genre to come to with an artificial planet. Do something that relates to sci-fi, like technology, space travel, or extra dimensions/universes. If you're programming a fantasy game, then you should use something that relates to: castles (they were found in Medieval Europe and Japan), barbarians (Mongols, Vikings, Caribs...), Magic, and basically anything that came before The Modern Age.
You may even want to make more changes to your location. If so, then think, "What will I use this location for?". The location's basic layout (and possibly it's theme) should be related to it's role in your game. If it is the final level, it must be harder than normal, and it must relate to the end boss (see the creatures section) of the game. If it is the first level of the game, it should have a tutorial built into it somehow, and it should be easier than normal. For example, if I took the villain that I created in the section about creatures, and I made him the final boss of my game, I should model the final level (in which you kill the end boss) after the bat creature. My plan was that the bat creature was scary and bat-like, so the level should be scary and it should resemble a bat's natural habitat in real life - a cave.
Here are some examples of items from other games and what they do:
Think, "What goal do I want this item to help the player accomplish?". The item should look like something that would help you achieve something similar in real life. Example: trampolines help you bounce higher, shovels help you dig into the ground, skateboards help you travel faster...
Remember the one rule when using this method: Don't be offensive to another culture. Examples of this method are: