When I'm working on my various sage-ability tables, I am anxious not to duplicate abilities that already exist among the considerable list of spells, existing magic items, ability stats and in the background generator I've created (though there is intentional overlap with the latter in many cases). Obviously, this isn't easy or even always possible ~ but that is the goal. Moreover, I'm highly resistant to giving straight combat or ability stat bonuses for anything. The combat system in the game is so fine-tuned, I don't want characters having the option to bully up on extra to-hit and damage modifiers, such as what happened with the development of super-classes in the 1980s before 2nd Edition, ultimately carried through all the editions that came after that were designed to create super-heroes instead of characters.
As such, those rules to which I've clung greatly thins down much of Dani's list. I've got many elements already that add to morale (04); I don't want anything that fuels magic or resembles a magic item (06, 07, 36, 37, 38, 39, 40) or combat prowess (20, 50); it can't duplicate an actual spell (08, 15, 22, 29, 30, 31, 32, 33, 34, 41, 42, 46, 47, 48, 49) or a character/class ability (09, 11, 12, 13); and certainly nothing that flat out adds to a character's experience (10). I am somewhat uncomfortable with any effect that compels a character to betray a particular emotion (16, 17, 18, 19), as it is very hard to employ against a player character to the same degree as an NPC. Those discarded things, however, are the lowest hanging fruit. It is easy to give more bonuses to weapon damage or to offer another light source; what's wanted are truly original ideas, the sort that demand original rules. In this Dani excels, regarding the rest of her list:
1 Increases happiness in 1 mi radius when accessible
2 Fires burn hotter in the vicinity
3 Plants flourish, harvest is especially fruitful (yield increased by 25%)
5 Revitalizes: when resting in its view, 1 extra hp/HD recovered
14 Shortens magical research time
21 Training times shortened
23 Shortens construction time
24 Increases the quality of metal goods produced nearby
25 Increases the quality of wooden goods produced nearby
26 Increases the quality of stone goods produced nearby
27 Mineral veins more fruitful - mine 25% more resources than usual
28 People get intoxicated more easily near the artwork
35 Animals attracted to the object
43 Holy: attempts to communicate with the Divines are more likely to succeed
44 Sacrosanct: Area within 50' of artwork is sacred ground (as a temple)
45 Unhallow: Area within 50' of artwork is unholy ground, providing benefits to undead creatures
We can group these things into types: those that change the social climate (01, 28, 35); those that alter fixed nature (02, 03, 24, 25, 26, 27); those that increase vitality (05, 14, 21, 23); and those that adjust the divine (43, 44, 45)
These are each things that are largely ignored by most role-playing incarnations. Whereas "nature" is often influenced by spells or magic items, those changes are largely elemental in form, NOT commercial. Plant growth says nothing about ripening crops or fruits, there is nothing written about making trees easier to cut down or to make stone softer and easier to carve and shape. Yet this is what we want to concentrate upon, since we want to see the world as bards see it. Splitting even stone blocks from the side of a mountain to make them useful as materials is much more important than changing rock to mud. What good is mud to a bard? What good is stone that has been twisted and shaped, if it loses the cleavage and luster that gives sculpture its vivaciousness? A bard isn't interested in warping nature, a bard's goal is to enhance what already exists, to produce ease of expression and the greater capacity for bang and audacity.
In regards to social climate, why do people get more intoxicated near the artwork? Is it the artwork, or is it really what the artwork affects groups of people together. Here we need to think of the artwork as a song or a great poem, where the common room of a roadhouse grow closer together in the dim firelight, transformed from lonely individuals to a beloved collective through the words of the bard; where the intoxication that is obtained isn't a falling down drunk starting a bar fight, but three score people all incomprehensibly happy and soused to the gills.
What is "happy"? How does that play in a game? We have a tendency to think it means cutting the prices at the inn or maybe free stuff, but I think it is, rather, the willingness to give audiences to strangers, to find room at the inn where there is no room, to sacrifice a little self-comfort because another being is in distress. It is the cleric, not being asked, seeing a character badly beat up and turning up to give an unsolicited cure spell; it is a bartender gently warning the party that the draft is much more intoxicating than they might think; it is the guards turning up, rounding up the party and then letting them go with a warning. It is a dozen different ways to make people feel welcome and safe ~ exactly what every town in a D&D world never tries to do.
Why shouldn't a great artwork make people happy like that? A cathedral, perhaps, or a great park in the middle of the town, where there are comfortable green lawns to lay upon near fresh water, designed by some bard interested in city planning (don't scoff, this was done often in many parts of the world as far back as three millenia ago).
We want to get out of the "spell/ability" framework in what a bard does. We have other character classes to do those things. The bard has to be different - has to fill a role that no other class can. When we think of the abilities that a bard has, we have to stretch ourselves out of what's easy to create and try for what an artist would want, if an artist could transform the world the way a mage can.