This is a hard project I'm workin' on and I'd really like to get some help, maybe even the help of the "bosses". :)
This is a very concrete mechanic to add another level of depth to character building.
Again, this is far from complete or perfect..But it's a starting point. :)
What is a theme?
A theme is a general description of your character: it helps to give strength to the concept and add some mechanical benefit to what usually is just fluff. A theme is something similar to a specialization, something that your character is very good at: it can be a profession or, even better, a "vocation".
To get a theme, I suggest to make a little bargain.
A theme gives you strong features at 1st, 4th, 7th and 10th level: at those levels, you give up a feat.
At a certain point of your life, you can choose to change your apirations and maybe you're not interested in the theme anymore: a GM should allow to exchange feats with theme features, as well as the opposite, if needed.
I'll write down some of the themes I'm creating. They're not meant to be perfectly balanced: they need to be flavourful and still funny to play. They increase a little the power curve, but they leave the character on a manageable level.
1st level: Dragon Lore
You get a +2 bonus in all skill checks invoving Dragon-like creatures lore.
4th level: You're my Quarry, stupid Lizard!
Dragon-like creatures are vulnerable to your attacks.
7th level: Oh yeah, You're scales are sooo sweet!
You get a +2 bonus to attack rolls and damage rolls against dragon-like creatures.
10th level: That's predictable!
Once per day, you can "decide" to avoid a Dragon-like creature attack. Yeah, even a Breath attack.
1st level: Expert Healer
You get a +2 bonus to all skill checks involving wounds and illness treatment.
4th level: Hand of the Gods
You gain the ability to cast the "Cure Wounds" spell. If you already have the chance to cast it, you can cast it twice per day.
7th level: That's just a scratch
Every time you heal damage, the target regains additiona hit points equal to your level + your charisma modifier.
10th level: Healer's Mercy
Once per day, you can cast any one healing spell you know without expending a slot.
1st level: That's in my Blood
Choose an Animal of your size or lower (everything in between a spider and a wolf). You can communicate freely with all the animals of the chosen type.
4th level: Something's Changin'
Once per day, you can assume a single trait of the chosen animal (as the ability to see through darkness of a howl). If you acquire an in-combat ability (like bites or claws), you can use them as alternate attacks. Once per battle, you can use such an attack as a quick action. You and your GM should get some inspiration from the monster section of the core book or the Bestiary.
7th level: Ok...I got it...I'm...
Once per day, you can turn into the chosen animal as a standard action. You get all of its abilities and features. You can't use any ability you have in yoru standard form. You can retain this form as long as you like.
10th level: That's definitely...ROOOOARR!
You can switch through your forms as many times as you like, using a standard action every time. Have fun.
ALCHEMIST (see the "Alchemical Stuff and Potions" content I've submitted)
Special: you always need some Alchemist tools in order to prepare stuff...
1st level: Put this, than this and than...
Once per day, you can create an Alchemical object or Potion of your tier. You expend a number of gold piecec equal to the object's cost. Requires 1 hour of work.
4th level: And now this, and this...
You can now create two objects of the same type in a single hour of work or two different potions in separated work sessions. You pay each object's cost.
7th level: I really need that plant!
You can spend an hour looking for components and get some materials to reduce the amount of money needed to brew potions or create objects. At the end of the research, make a Wisdom skill check with a +2 bonus (variable DC). On a success, you've got useful stuff. As long as you have those materials, you can decide to use them to halve the cost of ALL of the objects you create in a single day.
10th level: Hi, My name's Fulcanelli.
After an hour, you can transform an object into another of the same category (see below).
Healing Potion (or similar) <--> Poison (or similar)
Explosive <--> Protective
non-healing Potion <--> non-healing Potion
At GMs discreption, some changes can be impossible.
1st level: Come on, men!
At the start of a battle, you can make a Charisma check with a +2 bonus (or a relevant background). Each nearby ally who can see or hear you with a MD equal or lower the result of yuor check gets a +1 to attack rolls until the end of the battle.
4th level: Keep on fighting!
Once per battle, you can spend a standard action to encourage your nearby ally who can see or hear you. If you do, they can heal using a Recovery and add your charisma modifier to the hit points they regained.
7th level: One more!
Every time you or an ally drop a non-mook enemy to 0 hit points or lower or every time you or an ally score a critical hit against a non-mook enemy, you can spend a move action to engage another non-mook enemy on your next turn, screaming to your allies. The crit range of each nearby ally who can see or hear you screaming expands by 1 (up to +4) until the end of the battle.
10th level: Not today. Not now.
As long as you're vigilant and lucid, you can spend a quick action on your turn to encourage your nearby allies. If you do so, each ally who can see or hear you gain temporary hit points equal to your charisma modifier + your level.