Congratulations, you have successfully made your way to the (arguably) trickiest part of game designing, choosing a theme.

What are themes? The theme is the concept of the life of your game.

Some of the tips I am about to share with you will guide you through the process of choosing an appropriate theme for your game!

1. What type of game is it?

MMO? RTS? FPS? RPG? These are all major genre's in games today, that's why is is EXTREMELY difficult to create a game like this that is both unique in terms of gameplay as well as theme.

EVERYBODY knows about the typical fantasy mmo/rpg, or the infamous WW2 based FPS's which their are countless renditions. These are NOT original themes at all and game designers/developers should stay away from themes that aren't highly unique.

Be unique.

2. What does your development staff consist of?

You may be thinking "What type of question is this?!" but I'm here to tell you that development staff has a fair bit to do with theme choice. Picking broad and cliche themes will require a bigger or highly professional work staff.

This is because it takes more effort into trying to create something non-original than it does something very original. Don't believe me?

It is a known fact that big-name companies in the gaming industry create games that have generic themes with standard gameplay.
If you are an indie developer, you know that if you try to compete with these "big dogs", you will be trampled by their paws.

In order for your game to be popular, you MUST stay away from standard/traditional themes, leave those to the bigger corporations.

(Indie game development is known for thinking outside the box, thats why many games like Tribes Ascend are very successful, their isn't an game like it)

3. What are you interested in?

This is a major factor when it comes to theme decision. Picking a theme you like will motivate you to create a game you would like to play as well as make!

4. What is an ideal setting for your game?

Finding an appropriate location for your game can be a struggle that is why many game developers use bland settings.

What I want you to do: Find a good setting for your game, then go to google and type in: "fantasy worlds". Scroll though the pages, look at every image until you find one that really strikes you. Go to the rest of your team and ask them what they think, if they like it, then go for it and don't hold back!

5. If you are afraid of being judged, you will not make it far in this industry.

I hope I helped those of you who were having trouble with this tricky area of game developing. If you have any other questions regarding game design, please contact me and I'de be glad to help!
Thanks!

These are rad thanks. To help exercise my theme building I find the method I like to use is on the way home from work. I turn on the radio to a station I can't stand (generally) and I turn a song (I most likely would never listen to otherwise) into a game. Every song, no matter how shallow, sets a mood or paints a picture with sound. Using someone else's poetry or sound to build your own visual experience helps to remove at least one of the many barriers a designer has to overcome. Pressure under fire is the way I like to work and using the length of a song to build design ideas forces me to be creative while relying on ideas I know will work. Old songs I already know aren't really ideal because I've build plenty of games while listening to them. It has to be something you're not used to listening to and maybe even don't want to listen to. This forces your mind to explore aspects you aren't used to considering (search for uniqueness). A little background info on this process, I started doing it when I was carpooling with people who played the worst music while we drove home. I realized creating games in my head was a good distraction and decided to just keep doing it.

I find the more I do this time killer, the more streamlined my design process became and I end up using the a lot of the same systematic design processes to design game ideas naturally as well.

I'm not sure if this would work for everyone but since it's helped me build themes I thought I share it here. Again, great post!

Uhm... never had a problem coming up with an idea for a game. I either come up with an interesting game mechanic I want to try, setting I want to explore or a character (and, well, the setting where that character can shine comes to me as if it was attached to the character).

Also, I've made it into a habit to write down my ideas whenever I get them, so maybe that's why I don't have problems finding new ones.

Be unique.[/quote]
Uhh... yeah... awesome advice. I'm sure it'll open the eyes of many out there.

I think your advice is a little broad and unspecific. You know, nothing that doesn't seem obvious to most people.
I guess what most aspiring game developers would like to read are inside stories, little tips and tricks, something you have learned from personal experience.

Also to me the term "theme" has to be dissected into theme and genre. Themes are for me things like: SciFi, Medieval, Horror, Zombies, Warfare, etc.
And then you have the different genres: FPS, RPG, Jump'n'run, ...

You are right with the tip, not to try and compete with the big players in cliché theme/genre/art combinations.
If you go that road you are destined to fail. You'd have to reach the level of polish of the blockbuster game in that area, plus "then some".
Simply because people WILL choose Call of Duty 17 over your game if you don't offer ONE unique and interesting aspect.

If I had to give only one advise, I guess it would be: Scale it down. And focus one your ONE unique selling point.

I am not going to go as far and say you are wrong, but perhaps you are over-complicating the idea here.

I believe a theme for a game should be simple, summed up in as few words as possible. Once the theme is decided upon everything in the game should support it however possible. Portal (1 and 2) is a good example.

I believe the theme of the Portal games is minimalism.

It isn't testing, or puzzles, or the portals themselves, it is minimalism (IMHO).

You see this everywhere:

• The story (I enjoy the story, but one must admit, it is
  
• The characters (a minimal number for each game)
  
• The dialogue (only one speaker in the first game, three in the second (and one is never seen in "the flesh"))
  
• The environment (clean, sterile and composed of simple shapes and colors)
  
• The UI (few colors, simple shapes)
  
  Another example might be Diablo - the theme is darkness and evil. Everything seems to exude a general feeling of darkness. This is seen in the gameplay, the UI and the cut scenes.
  
  These are what I believe good and effective themes are.

I think that you are approaching the theme topic from the wrong direction. Most people have not a problem to come up with a theme, they will most likely think of a story or some cool action scenes first, which already include a theme.

The really tricky way is to come up with a cool game not a cool theme. If you make a cool clone of an existing game with a niche theme, you will not attract a lot of people, because all the cool themes are already taken. Themes are one of the most appealing features of a game, taking a niche theme could be really turning down an otherwise good game.

I would even go as far as to say, that you can benefit from a popular theme. As example, making a FPS game in a WWII theme will only have success if you add something new to the game play. This way battlefield got quite popular by adding controlable vehicles to a FPS game, didn't it ?