This is an attempt to make a list of what "off-template" advantages are allowed purchases in DF Felltower.
I get a lot of requests for off-template advantages. Lifting ST is the most popular request, but it's followed frequently by Fit, Enhanced defenses, "Strong Will" - a 3e-ism, and Fearlessness.
I've gotten occasional questions about stat limits - if your template doesn't list a bonus to a given stat at the level you want, is it "off-template?"
I get questions about skills, too, but that's a different (and shorter) post.
Here is a list of what you can add to your template:
Statistics & Secondary Characteristics
You are limited per your race per Dungeon Fantasy 11: Power-Ups, p. 5, modified for your template also per Dungeon Fantasy 11: Power-Ups. Remember template maxima are before racial modifiers. (For most templates, for a human, this is 20 in stats, secondary characteristics 20 or figured off of stats with a cap.)
Anything on your template can be added freely. They cost $40/point for a new advantage or to expand a current advantage. (In other words, buying Fearlessness 1 costs $40, 2 costs another $40, etc.)
Advantages are capped at the maximum level listed on a template - for example, Ridiculous Luck is only available to Bards and Swashbucklers even though Luck and Extraordinary Luck are on other templates.
They cost $80/point for a new advantage advantage or to expand a current advantage unless specified otherwise.
The following traits are available for any delver, regardless of template:
Combat Reflexes 
Fit  (but not Very Fit)
Wealth [varies] (cost per this post.)
General Power-Ups - all those on pp. 10-13 are available as are the Utility Power-Ups on p. 16. All of these are "on template" for costs.
Casters also have access to Caster Power-Ups pp. 13-16 with the exception of Spell-Archery (not available.) Please note that "Psychic Guidance" is not being used; use Mystic Guidance instead.
- On template means on your specific template. If a related template has an advantage, that's not relevant. A regular Barbarian lacks Born War Leader and thus cannot get it even though it's listed on the Savage Warrior. You can't jump back and forth between the DF and DFRPG versions of your template, either, if they vary.
- Assuming cases are restrictive, not expansive. If it's not specifically listed, it's excluded.
- Specific power-ups for your template may also be off-limits; we're not using Wizard Hunter or Bow Fencer, for example, even though those are listed for some templates as a valid power-up.
- Some power-ups need specific external training (such as purchasing a Lens) or require an in-game explanation. These include Reputation - which must follow from in-game events, Claim to Hospitality - which also requires a solid in-game explanation, and Wealth - you need the money and the access to a town, effectively making it impossible to get for non-town-dwelling PCs.
Otherwise . . . that's it! I'm open to expanding the list if someone (meaning my players, for the most part) can point out a generically useful, logically generally available advantage I may consent to adding it.