Since I queried the idea in the rules and regulations thread, I guess it's only fair that I put in my 2 cents for the concepts that I'd like to see renovated.
I think there are concepts which have been imagined and re-imagined to death, and similarly there are concepts that have barely been touched on because they are too narrow in their definition. Everyone has different opinions on this though, due to concept exposure and depth of knowledge.
So I'm going to give a pair of personal ratings for different concepts (both on a scale of 0 to 3). The first rating (000, 00X, 0XX, XXX) is a scale of how much potential I feel is available in the concept. Narrow concepts like "African Magic Styles" get low ratings because there just isn't a lot you can do with them, wider concepts like "Vampires" get higher ratings because they can be applied to dozens of settings, and there is still plenty you can do with them.
The second rating (000, 00#, 0##, ###) is a scale of how many times this type of concept has been re-imagined or renovated in the past. The low ratings apply to things like "Elves", "Vampires" and "Martial Artists" which have been done to death in dozens of games, there may still be potential in them but trying to do something truly innovative, interesting and different will be a challenge. The high ratings would apply to things like "Elementals" and "Local Townsfolk" which get touched on in numerous systems, but they are usually left as bit parts, NPCs or occasional storyline elements.
Finally, I'll add together the ratings which would give a general difficulty factor in my mind for renovating this concept. The wider the scope, and the less it's been touched in other games; the easier it is to play with. The narrower the scope, and the more well defined in other games; the more challenging it would be. High numbers make easier subjects to do interesting, dynamic and unique concepts).
There are some pretty personal biases in here, so feel free to argue with me about these. I'm just giving an explanation for why I'd like to see certain concept renovated more than others. It would also be possible to add in other rating scores, but I've chosen not to go too heavily into this.
Cyborgs (00X, 00#) = 2 out of 6 [Fairly Hard]
I've seen a few games with cyborgs in them, and a bit of diversity with steampunk versions, mystically empowered cyborgs and other options, but I still think there's good potential to be explored.
Elves (0XX, 000) = 2 out of 6 [Fairly Hard]
I've seen a butt-load of elves in dozens of gaming products. Dozens of sub-races, numerous settings and plenty of sourcebooks that describe hundreds of racial aspects. There's probably still some scope in this one, but trying to find something new won't be easy.
Vampires (0XX, 000) = 2 out of 6 [Fairly Hard]
With an entire game dedicated to them (with dozens of sourcebooks), and an appearance in plenty of other systems vampires have been explored pretty thoroughly (from psychic vampires to blood drinkers and flesh eaters). I'm sure there are aspects that haven't been touched, but like elves getting something new from this subject will be tricky.
Robots (00X, 0##) = 3 out of 6 [Moderate]
Many of the games that include Cyborgs also include robots, but these are typically relegated to secondary roles. Robots tend to be a biot more specialised and focused, but I think there is plenty of potential to be explored here.
Dwarves (0XX, 0##) = 4 out of 6 [Fairly Easy]
Dwarves are often seen as the traditional enemies of elves and typically appear in the same settings, but while the elves have seen a lot of diversity I haven't seen as much stuff about dwarves. I think there is plenty of scope to played with in this category.
Goblins (00X, 0##) = 3 out of 6 [Moderate]
Goblins were once relegated to the role of cannon fodder, but with the rise of the steampunk setting, many new technological goblin options have appeared and the subject matter is being explored. It's getting harder to find new goblin concepts, but I'm sure there are still plenty around.
The Illuminati or Knights Templar (000, 00#) = 1 out of 6 [Very Hard]
Almost every conspiracy setting includes these groups, but historically they are very narrow and focused. There isn't a lot you can do with them while still calling them by these names. A broader category of "Secret Societies" might be easier to play with.
Shapeshifters (XXX, 0##) = 5 out of 6 [Very Easy]
In games where ther are werewolves, there are often other shapeshifters in hidden parts of the world which are used as antagonists or NPCs. A few games have tried to explore the concept of shapeshifters, but I haven't seen many do them well.
Magic Users (XXX, 000) = 3 out of 6 [Moderate]
Magic Users (and psychics) appear in the vast majority of gaming products, but the topic is virtually limitless in it's scope. Trying to develop new schools of magic for any setting would be pretty easy, but trying to make them unique and special becomes the true challenge.
Pirates (0XX, 00#) = 3 out of 6 [Moderate]
Once Pirates would have been an easy topic to explore, but now the subject matter is become so commonplace that new an revolutionary concepts are getting harder to find. Pirates are appearing in numerous settings, but their scope as swashbuckling criminals is fairly narrow.
Totem Spirits (0XX, 0##) = 4 out of 6 [Fairly Easy]
There are only a few gaming systems I'm aware of that include the concept of Totems and the powers bestowed when pacts are made with them. A similar type of topic could be "Deals with the devil", which roleplaying has traditionally avoided due to over-zealous religious types.
Martial Arts (00X, 000) = 1 out of 6 [Very Hard]
Martial arts and those who practice them are found in every roleplaying game, so trying to milk this one for a new and dynamic concept is going to be nigh impossible.
Ninjas (000, 00#) = 1 out of 6 [Very Hard]
Like martial artists, Ninjas are found in plenty of systems usually as antagonists, but also as allies and plot elements. Historically, they are a very specific concept and trying to expand the idea to western societies tends to lead to "The assassin's guild" which is also a concept that has been done to death.
Nazis (000, ###) = 3 out of 6 [Moderate]
This one intrigued me. I guess it's a taboo topic like "deals with the devil", but the Nazis had plenty of supernatural influence happening. This has been explored in more depth through recent movies and pop culture, but I think there is still plenty of political and supernatural scope to play with.
I don't know if the concepts chosen will deliberately be those that are harder to work with, but as you can see from the scales above certain players will definitely have advantages over others with some subjects.