I play with colors. When I find a nice color that I like, I think what could be made from it. (e.g. What does the color symbolize? What does it mean to normal people? Where can you find this color?)
Very interesting..can you give some examples?
It's kinda hard to explain. Hmm...
First, I absorb inspiration from various sources. Nature, photography, digital art, other pixel art, youtube videos, etc etc.
Then I open a pixel editing program, and try to remember the things I liked on the sources. I might remember a cool color, a cool color scheme, an awesome color palette or color combinations.
So let's say I remember a nice tone of green.
Now, where would we see this color? - Almost everywhere. I know.
1. Try to find things and items around you that are almost like the color you found.
I found:
-My bible
-A calendar of year who-knows-what
-Wacom Bamboo-drawing board
-A little jar of vaseline
-Blanket
-My little brother's water gun
-A couple of green marker pens.
2. Now, what does this color symbolize?
-Happiness, maybe.
-Jealousy
-Life, nature
-Youth
-Balance
-Self-respect
-Green energy
-Green tea
3. Which counties have green in their flags?
(http://en.wikipedia.org/wiki/List_of_countries_by_colors_of_national_flags) as sourceFor example: Bolivia, Mali, Lithuania, Nigeria, Pakistan, Ireland, Idia, Jamaica, Macau
Now you can take a look at the cultures of these countries, or just see what comes in mind when you think about one of these. This is also good when trying to find a nice landscape/world.
4. Of course, you can always think about games. What comes to mind when you think about green?
-Wizards
-Lizards
-Dinosaurs
-Earth magic
-Slimes!
-Fantasy games
-Creeper
-Tall grass
-Goblins
-Neon lights
-Almost every single game with soldiers
5. You can now pick up things you were interested the most and then combine your results, and see if you get anything that inspires you.
-My little brother's water gun
-Life, nature
-Green energy
-Green tea -> Asia
>>> Located in a fictional Asian country, people (or maybe panda bears, that would be cool?

) fight against an international company that tries to destroy their green and peaceful home (Generic enemy, complete opposite).....aaand I think I'll let you do the rest.
TL;DR
I have no idea if this was helpful at all. I'm not very good at explaining my own methods and stuff. Plus, I've never actually released a game and I'm always out of good ideas.